Cheat Sheets

Python Cheat Sheet

Dave Child — Thu, 22 Jan 2009 13:29:00 +0000

Overview

The Python cheat sheet is a one-page reference sheet for the Python programming language.

If you like the cheat sheets, and want to say thanks, please consider buying me something from my Amazon Wishlist. Thankyou very much to those who have already hunted it down and sent me something - I'm very grateful!

Downloads

• PDF, 398Kb
• PNG, 90Kb

The Python Cheat Sheet is released under a Creative Commons License (Attribution, Non-Commercial, Share Alike).

Please note: If you wish to link to a cheat sheet from elsewhere, please link to this page so others find all available versions, the license and the description.

sys Variables

Python has a variety of built-in variables which give information about the system on which it is running.

sys.argv

sys.argv contains command line arguments in a zero-based list.

os Variables

In a similar fashion to the "sys" variables, Python also has built in variables which give information about the operating system on which it is running. This section also lists the "registered" OS names.

Methods

Python, as you might expect, has a huge variety of standard methods for working with strings, lists, files and classes, and this section lists those with, where possible, compulsory arguments.

Indexes and Slices

Indexes and slices have been known to trip up plenty of new programmers, and occasionally experienced programmers new to Python. This section of the cheat sheet shows by example how indexes and slices work in Python.

Date and Time

These sections of the cheat sheet include the DateTime and Time methods, as well as the various Date Formatting options available for the strftime and strptime functions.

Thanks

This is the second cheat sheet created with the involvement of the Cheat Sheets Google Group, and the first to include twitter (@CheatSheets). Many thanks to Charly Walther and Dan Horning for their suggestions and feedback. Finally, thanks also to the 1017 people who requested this cheat sheet!

Translations

Spanish / Español

Subversion Cheat Sheet

Dave Child — Thu, 07 Aug 2008 11:47:00 +0000

Overview

The Subversion (SVN) cheat sheet is a one-page reference sheet for Subversion on the command line.

Downloads

• PDF, 293Kb
• PNG, 97Kb

The Subversion Cheat Sheet is released under a Creative Commons License (Attribution, Non-Commercial, Share Alike).

Please note: If you wish to link to a cheat sheet from elsewhere, please link to this page so others find all available versions, the license and the description.

Subversion Components

Subversion is made up of several different parts. In addition to the svn command line program most people are familiar with, there are also utilities like svnlook and svnadmin, a server (svnserve) and an apache module.

Subversion Protocols

Subversion clients can connect to subversion servers over a variety of different protocols, including HTTP and SSH.

Subversion Help

If you ever find yourself stuck, of unsure of how a command works (and this cheat sheet is unable to help), check out "svn help" for general Subversion help, or "svn help command" for help with a specific command. Please note that command line commands will be marked with "$" on this cheat sheet. Explanations will be on the following line and italicized.

Repository Administration

This section of the cheat sheet shows some of the basic, and most commonly used, repository commands, starting with how to create a new repository.

Getting Started

The first thing you are likely to want to do with a brand new repository is add some files to it. For this, you will need the import command. If you want to create a local copy (usually referred to as a working copy) of a repository, you will need to checkout. And if you want to grab any changes to the repository, you will need to run an update.

Adding, Deleting, Copying and Moving

These sections of the cheat sheet outline basic file and folder operations: Adding, Deleting, Copying and Moving.

Revert Changes

If you want to undo changes you have made to your working copy (i.e., change it back to the way it was when you last updated it), you can revert changes.

Logs and Blame

Log files are what make version control systems useful, giving you a complete history of changes to a repository. The log command will show you all the changes to a path, and the blame command will show you the changes to a path with more specific information.

Diffs and Merges

The diff command shows you the difference between two files, while the merge command allows you to apply the diff between two files to a third one.

Commit

Commit is the command you will use most often when working with SVN, by far. It is the command you run when you want to send what you've changed back to the repository. You should always add a message with your commit, explaining the changes you are making.

Miscellaneous Commands

This section of the cheat sheet lists some of the lesser used Subversion commands, including cleanup - a command to resursively remove locks and complete unfinished operations (very useful when things go wrong) and resolve (when you are working on a file, but another developer has changed the file at the same time, you will have a conflict - this command is to be used when the conflict has been resolved).

Item and Property Statuses

If you run the status command on a path, you will see a list of letters (and blank spaces) for each item in the path. Each of these letters has a specific meaning and tells you something about the file you are viewing. This section lists those letters and their meanings.

Property Commands

Items in a Subversion repository have properties specific to SVN, and these properties can be added to, edited or deleted. This section lists the commands you will need in order to be able to work with properties.

Argument Shortcuts

Finally, almost every Subversion command takes a selection of arguments, and many of these have shortcuts. If you want to commit changes to a folder, but don't want to commit changes to its contents, you could type svn commit --non-recursive "/path", but it's much quicker just to use the shortcut -N instead of --non-recursive.

Thanks

Much of the content on this cheat sheet is based on the excellent SVN Book, available at http://svnbook.red-bean.com/. This is the first cheat sheet created with the involvement of the Cheat Sheets Google Group. Many thanks to Alan Switzer and Randy Merrill for their suggestions and feedback. Finally, thanks also to the 210 people who requested this cheat sheet!

Regular Expressions Cheat Sheet (V2)

Dave Child — Mon, 30 Jun 2008 12:53:31 +0000

Overview

The Regular Expressions cheat sheet is a one-page reference sheet. It is a guide to patterns in regular expressions, and is not specific to any single language.

This is the second version of the Regular Expressions cheat sheet. The previous version can be found at http://www.addedbytes.com/cheat-sheets/regular-expressions-cheat-sheet-version-1/.

Downloads

• PDF, 648Kb
• PNG, 78Kb

The Regular Expressions Cheat Sheet is released under a Creative Commons License (Attribution, Non-Commercial, Share Alike).

Please note: If you wish to link to a cheat sheet from elsewhere, please link to this page so others find all available versions, the license and the description.

What's New?

There are a few small changes from the first version of the Regular Expressions Cheat Sheet (which you can still download if you prefer). The most obvious change may be that it now looks different. Hopefully it's now clearer and a little easier to find the information you're looking for.

About This Guide

I have included a little more detail in this document where I felt it would be helpful to those less familiar with regular expressions, to demonstrate some of the items on the sheet. Please feel free to let me know if any additions would be helpful.

Please also note that not everything on this sheet will work with every language that has regular expression support. Different languages use regular expressions in different ways, and in some, support is incomplete.

Anchors

Anchors in regular expressions refer to the start and end of things. This can be, for example, a string or word. These characters and symbols represent these anchors in regular expressions. For example, a pattern that matched a string that started with numbers might be the following, where "^" represents the start of the string.

^[0-9]+

Without the "^" symbol, the pattern would match any string with a digit in it.

Character Classes

Character Classes in regular expressions match a selection of characters at once. For example, "\d" will match any digit from 0 to 9 inclusive. "\w" will match letters and digits, and "\W" will match everything but letters and digits. A pattern to indentify letters, numbers or whitespace could be:

\w\s

POSIX

POSIX is a relatively new addition to the regular expressions family, and is quite similar to the idea behind character classes, allowing you to use a shortcut to represent a particular group of characters.

Assertions

Almost everyone has some trouble with assertions at first. They are tricky to get to grips with, but once you are familiar with them, you will use them alarmingly often. They provide a way to say "I want to find out every word in this document with a q in it, as long as that q isn't followed by 'werty'".

[^\s]*q(?!werty)[^\s]*

The above code starts by matching non-whitespace characters ([^\s]*), then a q (err ... q). Then the parser reaches the lookahead assertion. This makes the q conditional. The q will only be matched if the assertion is true. In this case, the assertion is a negative assertion. It will be true if what it checks for is not found.

So, it checks the next few characters against the pattern it has (werty). If they are found, the assertion is false, and so it will "ignore" the q - it will not match. If it doesn't find "werty", the assertion is true, and the q is matched. It then carries on checking for non-whitespace characters.

Sample Patterns

Finally, there is a selection of sample patterns. These patterns are intended to allow you to look at how regular expressions might be used in day-to-day work, and the various ways you can use regular expressions. Please note, however, that they will not necessarily work in every language, as each has its own idiosyncracies and varying support for regular expressions.

Quantifiers

Quantifiers allow you to specify a part of a pattern that must be matched a certain number of times. For example, if you wanted to find out if a document contained between 10 and 20 (inclusive) of the letter "a" in a row, you could use this pattern:

a{10,20}

Quantifier are "greedy" by default. So the quantifier "+", which means "one or more", will match as many items as possible. This can be a problem on occasion, so you can tell a quantifier to not be greedy (to be "lazy"), using a modifier. Consider the following code:

".*"

This will match text contained in quotation marks. However, you may have a string like this:

<a href="helloworld.htm" title="Hello World">Hello World</a>

The pattern above will match the following from the above string:

"helloworld.htm" title="Hello World"

It has been too greedy, matching as much text as it could.

".*?"

The above pattern will also match any characters contained in quotation marks. The non-greedy version (note the "?" modifier) will match as little as possible of the string, so will match each item in quotation marks separately:

"helloworld.htm""Hello World"

Special Characters

Regular expressions use symbols to represent certain things. However, that presents a problem if you want to detect a character in a string where that character is a symbol. A period (".") for example, in a regular expression, represents "any character except the new line character". If you want to find a period in a string, you can't just use "." as a pattern - it will match just about everything. So, you need to tell the parser to treat the period as a literal period rather than a special character. This you do with an escape character.

An escape character precedes the special character and tells the parser to ignore what follows. There are certain characters that will need to be escaped in the majority of patterns and languages, and you can find these characters listed at the bottom right of the cheat sheet.

The pattern to match a period is:

\.

Other special characters in regular expressions represent unusual elements in text. New lines and tabs, for example, can be typed using a keyboard, but are likely to trip up programming languages. The special characters use the escape character as well, to tell the regular expression parser that the following character is to be treated as a special character rather than a normal letter or number.

String Replacement

String replacement is covered in more detail in the "Groups and Ranges" section below, however one small point to note is the existence of "passive" groups. These are groups that are ignored for the purposes of replacement. This is very useful when you want to match something that requires an "or" section, but don't want it in the replacement.

Groups and Ranges

Groups and ranges are very very useful. Ranges are perhaps the easiest place to begin. They allow you to specify a selection of characters to match. For example, if you wanted to see if a string contained hexadecimal characters (zero to nine and a to f), you would use this range:

[A-Fa-f0-9]

If you wanted to see if a string did not contain the same, you would use a negative range, which in this case will match any character that isn't zero to nine or a to f.

[^A-Fa-f0-9]

Groups are essential to regular expressions, and are most often used when you want to use "or" in a pattern, or you want to reference part of a pattern later in the same pattern, or where using regular expression string replacement.

To use "or" is very simple - the following will match "ab" or "bc":

(ab|bc)

If you want to reference a previous group in a regular expression, you would use "\n", where "n" is the number of the group. You might need a pattern to match "aaa" or "bbb", followed by numbers, followed by the same 3 letters, and this would be done with groups, like so:

(aaa|bbb)[0-9]+\1

The above matches "aaa or bbb", and groups the match with the brackets. This is followed by a pattern for one or more numbers ("[0-9]+"), then finally "\1". The "\1" backreferences the first group, and looks for the same thing. It will match the matched text from the string, not the pattern, so "aaa123bbb" will not match the above pattern, as the "\1" will be looking for "aaa" to follow the numbers.

String replacement is one of the most useful tools of regular expressions. You can use "$n" to reference groups matched with the pattern when replacing text. Let's say you are want to make every instance of the word "wish" bold in a block of text. You would use a regular expression replacement function for this, which might look a little like this:

replace(pattern, replacement, subject)

The pattern is first, and would be something like the following (you would need a few extra characters for this specific function.

([^A-Za-z0-9])(wish)([^A-Za-z0-9])

This will find any instance of the word wish where it is preceded and followed by any non-alphanumeric character.

Your replacement can then be:

$1$2$3

This replacement will replace the whole pattern matched above. We start with the first character matched above ($1) (the first non-alphanumeric one), otherwise we'll be deleting characters from the block of text. The same applies at the end ($3) of the match. In the middle, we add the HTML tags for bold text (though you should use CSS or , of course), with the second group matched in the pattern ($2).

Pattern Modifiers

Pattern modifiers are used in several languages, most notably Perl. These allow you to change how the parser works. For example, the "i" modifier will tell the parser to ignore case.

In Perl, regular expressions contain the same character at the beginning and end. This can be any character at all (often "/"), and is used like so:

/pattern/

Modifiers would be added at the end of this, like so:

/pattern/i

Metacharacters

Finally, the last section of the cheat sheet lists the meta-characters. These are the characters that have special meaning in regular expressions, so if you want to use them literally, they must be escaped.

So, if you wanted to match test consisting of a bracket, you would need to use the following pattern:

\(

Translations

Italian / Italiano

mod_rewrite Cheat Sheet (V2)

Dave Child — Mon, 30 Jun 2008 12:37:14 +0000

Overview

The mod_rewrite cheat sheet is a one-page reference sheet, listing flags for the RewriteRule and RewriteCond directives, list of server variables, a regular expression guide and several examples of common rules.

If you're new to URL rewriting with mod_rewrite, you might find my article on URL Rewriting for Beginners useful.

This is the second version of the mod_rewrite cheat sheet. The previous version can be found at http://www.addedbytes.com/cheat-sheets/mod_rewrite-cheat-sheet-version-1/.

Downloads

• PDF, 563Kb
• PNG, 71Kb

The mod_rewrite Cheat Sheet is released under a Creative Commons License (Attribution, Non-Commercial, Share Alike).

Please note: If you wish to link to a cheat sheet from elsewhere, please link to this page so others find all available versions, the license and the description.

What's New?

There are a few small changes from the first version of the mod_rewrite Cheat Sheet (which you can still download if you prefer). The most obvious change may be that it now looks different. Hopefully it's now clearer and a little easier to find the information you're looking for.

Regular Expression Syntax

URL Rewriting with mod_rewrite depends a great deal upon a solid knowledge and understanding of regular expressions. The "RewriteRule" uses regular expressions in patterns extensively. This guide outlines the basic syntax of regular expression.

RewriteRule and RewriteCond Flags

Rewrite Rules in mod_rewrite can have flags appended to them, indicating to the server how the action described by the rule should be taken. For example, the 'L' flag tells the server not to process any more rules if the current rule is used.

Conditions in mod_rewrite can also have flags appended to them, and again these tell the server how to interpret the current condition. The "NC" flag indicates the condition is case-insensitive, and an "OR" flag between conditions tells the server that the following rule should be applied if any of the preceding conditions are true. The default in mod_rewrite is that, if a rule is preceded by a list of conditions, it should only be applied if all conditions are met.

Redirection Header Codes

When redirecting users with mod_rewrite, sometimes a status code must be sent back to the user. This status code is interpreted by the browser - sometimes it will mean the user is sent on to a new page, sometimes that they are shown a message. This section lists the most commonly used status codes with their meanings.

Example Rules

This section lists a few of the most situations mod_rewrite is used for, along with a rule to achieve the desired affect.

Server Variables

Sometimes it is necessary to rewrite URLs based upon variables like the referring URL or the browser being used. These variables can be used in mod_rewrite (including in the RewriteRule or RewriteCond sections), and this section lists the variables available.

Directives

mod_rewrite gives the server a series of instructions, called directives. For example, "RewriteEngine On" tells Apache that RewriteRules may be used and to interpret them if found. This section simply lists the directives used by mod_rewrite.

Other Formats

Text Version

PHP Cheat Sheet (V2)

Dave Child — Mon, 30 Jun 2008 12:24:30 +0000

Overview

The PHP cheat sheet is a one-page reference sheet, listing date format arguments, regular expression syntax and common functions.

This is the second version of the PHP cheat sheet. The previous version can be found at http://www.addedbytes.com/cheat-sheets/php-cheat-sheet-version-1/.

Updates

July 31st, 2008: Some typos corrected and more examples added to date section. Thanks to Simon Hollingshead for spotting the mistakes and for the suggestions.

Downloads

• PDF, 556Kb
• PNG, 81Kb

The PHP Cheat Sheet is released under a Creative Commons License (Attribution, Non-Commercial, Share Alike).

Please note: If you wish to link to a cheat sheet from elsewhere, please link to this page so others find all available versions, the license and the description.

What's New?

There are a few small changes from the first version of the PHP Cheat Sheet (which you can still download if you prefer). The most obvious change may be that it now looks different. Hopefully it's now clearer and a little easier to find the information you're looking for.

The content is largely unchanged. The Superglobals list has been removed, and the "function argument orders" section has been changed. Rather than list the orders by themselves, I have expanded the function lists to include function arguments where possible as well.

Function List

Probably the biggest problem with PHP is its inconsistency. Some function names use underscores, some don't. Some are of the form "verb object" and some are "object verb". Some use "2" instead of "to". These sections of the cheat sheet list many of the most commonly used functions in PHP and are there to provide a quick reference to check function names. These lists include arguments where possible, as PHP's argument ordering is inconsistent between similar functions.

fopen() Modes

fopen() is a widely used function and has several modes in which it can operate, depending on whether you want to read or write to a file, and what you want to do with data already in that file. This section lists those modes and what each does.

Regular Expression Syntax

Many people have trouble with regular expressions, and the first step to coming to grips with them is to become familiar with the various symbols used in regular expressions and their meaning. This section lists these symbols and describes their meaning.

PCRE Modifiers

"PCRE" stands for "Perl Compatible Regular Expressions". In PHP, this refers to functions like "preg_replace" and "preg_split". The patterns used in these functions can have modifiers applied to them, and this section list those modifiers and what they do.

Date Formatting

There are, as I'm sure you are aware, a huge number of options when it comes to date formatting, and there are few people who remember all of them. This section of the cheat sheet lists the various options, followed by a description, and an example where appropriate.

Translations

Italian / Italiano

Other Formats

Apple Dashboard Widget

CSS Cheat Sheet (V2)

Dave Child — Mon, 30 Jun 2008 11:33:55 +0000

Overview

The CSS cheat sheet is a one-page reference sheet, listing all selectors (as of CSS 2.1) and properties. It includes a visual example of the box model, unit reference for CSS units and the various media types CSS makes allowance for.

This is the second version of the CSS cheat sheet. The previous version can be found at http://www.addedbytes.com/cheat-sheets/css-cheat-sheet-version-1/.

Downloads

• PDF, 316Kb
• PNG, 77Kb

The CSS Cheat Sheet is released under a Creative Commons License (Attribution, Non-Commercial, Share Alike).

Please note: If you wish to link to a cheat sheet from elsewhere, please link to this page so others find all available versions, the license and the description.

What's New?

There are a few small changes from the first version of the CSS Cheat Sheet (which you can still download if you prefer). The most obvious change may be that it now looks different. Hopefully it's now clearer and a little easier to find the information you're looking for.

The content is largely unchanged. The syntax block has been removed, as have the media types - both were, according to feeback, largely useless. Removing them allowed me to change to a three column layout, making the properties lists far more prominent and useful.

Selectors

Given the number of possible selectors in CSS, it is no wonder some people often become confused. Mixing up ID and Class selectors is easy enough, without throwing sibling, child, attribute and language selectors into the mix. This section of the cheat sheet lists selectors and shows which element(s) those selectors would apply to.

Pseudo-Selectors

Pseudo-selectors are used when defining styles for elements that either do not exist, or are in a particular state. This section lists various of the pseudo-selectors.

Please note - I have left the :before and :after pseudo-selectors off this list, as I felt generated content was too complex to add to this sheet and still define in a way that made that area of the sheet usable.

Units

CSS allows the author to define dimensions and colours in many different ways, which can be especially useful when combined with media types. This section of the sheet lists the various units in CSS and explains what they mean.

More information on units in CSS.

Box Model

The box model is one thing that consistently trips up those new to CSS. Apart from major browsers not all supporting it correctly, its definition can be at first confusing. The box model section of the page aims to make this clearer.

Properties List

The CSS specification includes a lot or properties, many of which are often forgotten or overlooked. Many of these are shorthand properties, defining many properties in one go. The outside columns of the cheat sheet list all available CSS properties.

Translations

Other Formats

SQL Server Cheat Sheet

Dave Child — Fri, 20 Jul 2007 13:51:25 +0000

The SQL Server cheat sheet is a one-page A4 printable document, designed to provide a quick reference for SQL Server. A description of what is on the cheat sheet follows, or if you are impatient, you can go straight to the full size SQL Server cheat sheet.

It's been a while since my last cheat sheet release. But what could be better than to get the ball rolling again with the most requested cheat sheet not yet created (until now) - SQL Server. Microsoft's database engine is the source of many arguments between developers, but whether or not you believe another database to be superior, SQL Server is undoubtably powerful and includes some great management tools (Enterprise Manager, Query Analyser and the more recent SQL Server Management Studio) missing from comparable technologies.

Data Types and Conversion

SQL Server supports a large variety of data types and good database design relies in part on using the right data type for the right column. This section lists the data types available in groups. I've also included the syntax for the CAST and CONVERT functions here for convenience.

Functions

SQL Server has a large array of built in functions of varying use. This section includes string, date, mathematical, grouping, ranking and table functions. Alongside the date functions block there is also a run down of the different "dateparts" - the characters used in date functions to denote different periods (day, week, month etc).

Creation

Finally (short description for this cheat sheet!), the third part of the cheat sheet contains sample code for the creation of stored procedures, views, triggers, indexes and functions (the last of which I don't make nearly enough use of).

Download

The cheat sheet is available in two formats, PNG and PDF:

And finally, if you like the cheat sheets, and want to say thanks, please consider buying me something from my Amazon Wishlist. Thankyou very much to those who have already hunted it down and sent me something nice - I'm very grateful!

HTML Cheat Sheet

Dave Child — Mon, 08 Jan 2007 15:15:13 +0000

The HTML cheat sheet is a one-page A4 printable document, designed to provide a quick reference for HTML. A description of what is on the cheat sheet follows, or if you are impatient, you can go straight to the full size HTML cheat sheet.

In case you didn't already know, there is a complementary CSS Cheat Sheet available as well.

I have been working on this particular cheat sheet for a little over a year. It's been a tough one to put together - partly because of the wealth of information that could be included (a few colours and element attributes being the obvious items), and partly because it is difficult to know what web designers might find useful in an HTML cheat sheet.

Common Character Entities

There is a more expansive HTML Character Entities Cheat Sheet available, however that is more than many people need (or want), so I have included the most common character entity codes here as well.

Empty Tags

I have called the cheat sheet an HTML Cheat Sheet, however it is a little more complicated than that. HTML is an evolving language, and has passed through several incarnations. Most recently, use of XHTML has become more widespread. This cheat sheet is a useful tag reference for both HTML and XHTML. Empty tags exist within HTML however should not be closed with a trailing slash (i.e. ). In XHTML they must be closed. This section lists the empty tags for HTML and XHTML.

Attributes

Unfortunately, as the overriding principle of the cheat sheets is that they must be an easily printable single page A4 reference, I had far too little space to include all possible attributes for each element (though in future there may be a multi-page version that includes this information, if enough people are interested). However, I did have space to include some of the more important attributes. These sections include those core attributes.

Events

Events in HTML allow a developer to add client-side functionality to a page with JavaScript. While inline events are frowned on by those (including myself) who feel behaviour should be separated from content, they are still widely used and included here for that reason, broken down by type.

Download

The cheat sheet is available in two formats, PNG and PDF:

Update: 8 January 2006: The font issue should be resolved. If you were receiving a font error, please re-download the cheat sheet.

Please note: If you wish to link to the HTML cheat sheet from elsewhere, please link to this page so others find the description, rather than linking directly to the sheet.

Regular Expressions Cheat Sheet (V1)

Dave Child — Thu, 14 Sep 2006 09:16:00 +0000

There is a newer version of this cheat sheet!

The Regular Expressions cheat sheet is designed to be printed on an A4 sheet of paper and live by a designer or developer's desk, to make life a bit easier. A description of what is on the cheat sheet follows, or if you are impatient, you can go straight to the full size Regular Expressions cheat sheet.

Anchors

^[0-9]+

Without the "^" symbol, the pattern would match any string with a digit in it.

Character Classes

\w\s

POSIX

Assertions

[^\s]*q(?!werty)[^\s]*

Quantifiers and Quantifier Modifiers

a{10,20}

".*"

This will match text contained in quotation marks. However, you may have a string like this:

<a href="helloworld.htm" title="Hello World">Hello World</a>

The pattern above will match the following from the above string:

"helloworld.htm" title="Hello World"

It has been too greedy, matching as much text as it could.

".*?"

The above pattern will also match any characters contained in quotation marks. The non-greegy version (note the "?" modifier) will match as little as possible of the string, so will match each item in quotation marks separately:

"helloworld.htm""Hello World"

Escape Character and Metacharacters

The pattern to match a period is:

\.

Special Characters

Special characters in regular expressions represent unusual elements in text. New lines and tabs, for example, can be typed using a keyboard, but are likely to trip up programming languages. The special characters use the escape character as well, to tell the regular expression parser that the following character is to be treated as a special character rather than a normal letter or number.

Groups and Ranges

[A-Fa-f0-9]

If you wanted to see if a string did not contain the same, you would use a negative range, which in this case will match any character that isn't zero to nine or a to f.

[^A-Fa-f0-9]

To use "or" is very simple - the following will match "ab" or "bc":

(ab|bc)

(aaa|bbb)[0-9]+\1

replace(pattern, replacement, subject)

The pattern is first, and would be something like the following (you would need a few extra characters for this specific function.

([^A-Za-z0-9])(wish)([^A-Za-z0-9])

This will find any instance of the word wish where it is preceded and followed by any non-alphanumeric character.

Your replacement can then be:

$1$2$3

Pattern Modifiers

Pattern modifiers are used in several languages, most notably Perl. These allow you to change how the parser works. For example, the "i" modifier will tell the parser to ignore case.

In Perl, regular expressions contain the same character at the beginning and end. This can be any character at all (often "/"), and is used like so:

/pattern/

Modifiers would be added at the end of this, like so:

/pattern/i

String Replacement

String replacement has already been covered above, however one small addition to note is the existence of "passive" groups. These are groups that are ignored for the purposes of replacement. This is very useful when you want to match something that requires an "or" section, but don't want it in the replacement.

Sample Patterns

Download

So now that you know what it does, please feel free to print out the Regular Expressions cheat sheet:

Please note: If you wish to link to the Regular Expressions cheat sheet from elsewhere, please link to this page so others find the description, rather than linking directly to the sheet.

Microformats Cheat Sheet

Dave Child — Sat, 09 Sep 2006 19:03:14 +0000

Note: It turns out there is actually already a rather nice Microformats Cheat Sheet available (in PDF), by Brian Suda. That'll teach me to search for other cheat sheets before starting work on mine!

The Microformats cheat sheet is designed to be printed on an A4 sheet of paper and live by a designer or developer's desk, to make life a bit easier. A description of what is on the cheat sheet follows, or if you are impatient, you can go straight to the full size Microformats cheat sheet.

Further information on Microformats and their specifications can be found at microformats.org.

iCalendar and hCalendar

iCalendar is a common format for calendar documents on the web, and hCalendar is a microformat based upon the same standard. Essentially, it is a collection of attributes that allow you to identify events contained in an (X)HTML document. This section includes an example of an event in iCalendar and hCalendar formats.

hReview

hReview is a microformat that allows the marking up of reviews within (X)HTML documents. This section contains a sample review marked up with hReview.

vCard and hCard

vCard is a commonly used format for sharing contact details for people, and hCard is a microformat allowing you to mark up contact and personal information for people within web pages.

RelLicense and RelTag

RelLicense and RelTag allow you to add extra meaning to links within web documents, identifying links to licenses or that are used for tagging purposes.

XFN Format and Values

XFN is a microformat allowing you to identify relationships with people you link to within web documents, whether they are friends, family, co-workers or just people you once met. These sections show an example use of XFN, and a list of the valid values for XFN information.

Dates

Microformats use ISO 8601 format dates. This section details the specification, showing examples dates in their respective formats.

Download

So now that you know what it does, please feel free to print out the Microformats cheat sheet:

Please note: If you wish to link to the Microformats cheat sheet from elsewhere, please link to this page so others find the description, rather than linking directly to the sheet.