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Notebook

Sebastian Raschka

In [1]:
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In [2]:
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Last updated: 06/07/2014 22:50:23 EDTCPython 3.4.1IPython 2.1.0

I would be happy to hear your comments and suggestions. Please feel free to drop me a note via[twitter](https://twitter.com/rasbt), [email](mailto:bluewoodtree@gmail.com), or [google+](https://plus.google.com/+SebastianRaschka).

A collection of useful regular expressions



Sections



About there module

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The purpose of this IPython notebook is not to rewrite a detailed tutorial about regular expressions or the in-built Pythonre module, but to collect some useful regular expressions for copy&paste purposes.

The complete documentation of the Pythonre module can be found herehttps://docs.python.org/3.4/howto/regex.html. Below, I just want to list the most important methods for convenience:

  • re.match() : Determine if the RE matches at the beginning of the string.
  • re.search() : Scan through a string, looking for any location where this RE matches.
  • re.findall() : Find all substrings where the RE matches, and returns them as a list.
  • re.finditer() : Find all substrings where the RE matches, and returns them as an iterator.

If you are using the same regular expression multiple times, it is recommended to compile it for improved performance.

compiled_re = re.compile(r'some_regexpr')    for word in text:    match = comp.search(compiled_re))    # do something with the match

E.g., if we want to check if a string ends with a substring:

In [3]:
importreneedle='needlers'# Python approachprint(bool(any([needle.endswith(e)forein('ly','ed','ing','ers')])))# On-the-fly Regular expression in Pythonprint(bool(re.search(r'(?:ly|ed|ing|ers)$',needle)))# Compiled Regular expression in Pythoncomp=re.compile(r'(?:ly|ed|ing|ers)$')print(bool(comp.search(needle)))
TrueTrueTrue
In [4]:
%timeit -n 10000 -r 50 bool(any([needle.endswith(e) for e in ('ly', 'ed', 'ing', 'ers')]))%timeit -n 10000 -r 50 bool(re.search(r'(?:ly|ed|ing|ers)$', needle))%timeit -n 10000 -r 50 bool(comp.search(needle))
10000 loops, best of 50: 2.74 µs per loop10000 loops, best of 50: 2.93 µs per loop10000 loops, best of 50: 1.28 µs per loop


Identify files via file extensions

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A regular expression to check for file extensions.

Note: This approach is not recommended for thorough limitation of file types (parse the file header instead). However, this regex is still a useful alternative to e.g., a Python'sendswith approach for quick pre-filtering for certain files of interest.

In [5]:
pattern=r'(?i)(\w+)\.(jpeg|jpg|png|gif|tif|svg)$'# remove `(?i)` to make regexpr case-sensitivestr_true=('test.gif','image.jpeg','image.jpg','image.TIF')str_false=('test.pdf','test.gif.pdf',)fortinstr_true:assert(bool(re.match(pattern,t))==True),'%s is not True'%tforfinstr_false:assert(bool(re.match(pattern,f))==False),'%s is not False'%f


Username validation

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Checking for a valid user name that has a certain minimum and maximum length.

Allowed characters:

  • letters (upper- and lower-case)
  • numbers
  • dashes
  • underscores
In [6]:
min_len=5# minimum length for a valid usernamemax_len=15# maximum length for a valid usernamepattern=r"^(?i)[a-z0-9_-]{%s,%s}$"%(min_len,max_len)# remove `(?i)` to only allow lower-case lettersstr_true=('user123','123_user','Username')str_false=('user','username1234_is-way-too-long','user$34354')fortinstr_true:assert(bool(re.match(pattern,t))==True),'%s is not True'%tforfinstr_false:assert(bool(re.match(pattern,f))==False),'%s is not False'%f


Checking for valid email addresses

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A regular expression that captures most email addresses.

In [7]:
pattern=r"(^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+$)"str_true=('test@mail.com',)str_false=('testmail.com','@testmail.com','test@mailcom')fortinstr_true:assert(bool(re.match(pattern,t))==True),'%s is not True'%tforfinstr_false:assert(bool(re.match(pattern,f))==False),'%s is not False'%f



Check for a valid URL

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Checks for an URL if a string ...

  • starts withhttps://, orhttp://, orwww.
  • or ends with a dot extension
In [8]:
pattern='^(https?:\/\/)?([\da-z\.-]+)\.([a-z\.]{2,6})([\/\w \.-]*)*\/?$'str_true=('https://github.com','http://github.com','www.github.com','github.com','test.de','https://github.com/rasbt','test.jpeg'# !!!)str_false=('testmailcom','http:testmailcom',)fortinstr_true:assert(bool(re.match(pattern,t))==True),'%s is not True'%tforfinstr_false:assert(bool(re.match(pattern,f))==False),'%s is not False'%f



Checking for numbers

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Positive integers

In [9]:
pattern='^\d+$'str_true=('123','1',)str_false=('abc','1.1',)fortinstr_true:assert(bool(re.match(pattern,t))==True),'%s is not True'%tforfinstr_false:assert(bool(re.match(pattern,f))==False),'%s is not False'%f

Negative integers

In [10]:
pattern='^-\d+$'str_true=('-123','-1',)str_false=('123','-abc','-1.1',)fortinstr_true:assert(bool(re.match(pattern,t))==True),'%s is not True'%tforfinstr_false:assert(bool(re.match(pattern,f))==False),'%s is not False'%f

All integers

In [11]:
pattern='^-{0,1}\d+$'str_true=('-123','-1','1','123',)str_false=('123.0','-abc','-1.1',)fortinstr_true:assert(bool(re.match(pattern,t))==True),'%s is not True'%tforfinstr_false:assert(bool(re.match(pattern,f))==False),'%s is not False'%f

Positive numbers

In [12]:
pattern='^\d*\.{0,1}\d+$'str_true=('1','123','1.234',)str_false=('-abc','-123','-123.0')fortinstr_true:assert(bool(re.match(pattern,t))==True),'%s is not True'%tforfinstr_false:assert(bool(re.match(pattern,f))==False),'%s is not False'%f

Negative numbers

In [13]:
pattern='^-\d*\.{0,1}\d+$'str_true=('-1','-123','-123.0',)str_false=('-abc','1','123','1.234',)fortinstr_true:assert(bool(re.match(pattern,t))==True),'%s is not True'%tforfinstr_false:assert(bool(re.match(pattern,f))==False),'%s is not False'%f

All numbers

In [14]:
pattern='^-{0,1}\d*\.{0,1}\d+$'str_true=('1','123','1.234','-123','-123.0')str_false=('-abc')fortinstr_true:assert(bool(re.match(pattern,t))==True),'%s is not True'%tforfinstr_false:assert(bool(re.match(pattern,f))==False),'%s is not False'%f



Validating dates

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Validates dates inmm/dd/yyyy format.

In [15]:
pattern='^(0[1-9]|1[0-2])\/(0[1-9]|1\d|2\d|3[01])\/(19|20)\d{2}$'str_true=('01/08/2014','12/30/2014',)str_false=('22/08/2014','-123','1/8/2014','1/08/2014','01/8/2014')fortinstr_true:assert(bool(re.match(pattern,t))==True),'%s is not True'%tforfinstr_false:assert(bool(re.match(pattern,f))==False),'%s is not False'%f


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12-Hour format

In [29]:
pattern=r'^(1[012]|[1-9]):[0-5][0-9](\s)?(?i)(am|pm)$'str_true=('2:00pm','7:30 AM','12:05 am',)str_false=('22:00pm','14:00','3:12','03:12pm',)fortinstr_true:assert(bool(re.match(pattern,t))==True),'%s is not True'%tforfinstr_false:assert(bool(re.match(pattern,f))==False),'%s is not False'%f

24-Hour format

In [18]:
pattern=r'^([0-1]{1}[0-9]{1}|20|21|22|23):[0-5]{1}[0-9]{1}$'str_true=('14:00','00:30',)str_false=('22:00pm','4:00',)fortinstr_true:assert(bool(re.match(pattern,t))==True),'%s is not True'%tforfinstr_false:assert(bool(re.match(pattern,f))==False),'%s is not False'%f


Checking for HTML tags

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Also this regex is only recommended for "filtering" purposes and not a ultimate way to parse HTML. For more information see this excellent discussion on StackOverflow:
http://stackoverflow.com/questions/1732348/regex-match-open-tags-except-xhtml-self-contained-tags/

In [16]:
pattern=r"""</?\w+((\s+\w+(\s*=\s*(?:".*?"|'.*?'|[^'">\s]+))?)+\s*|\s*)/?>"""str_true=('<a>','<a href="something">','</a>','<img src>')str_false=('a>','<a ','< a >')fortinstr_true:assert(bool(re.match(pattern,t))==True),'%s is not True'%tforfinstr_false:assert(bool(re.match(pattern,f))==False),'%s is not False'%f



Checking for IP addresses

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IPv4

In [8]:
pattern=r'^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$'str_true=('172.16.254.1','1.2.3.4','01.102.103.104',)str_false=('17216.254.1','1.2.3.4.5','01 .102.103.104',)fortinstr_true:assert(bool(re.match(pattern,t))==True),'%s is not True'%tforfinstr_false:assert(bool(re.match(pattern,f))==False),'%s is not False'%f

Ipv6

In [21]:
pattern=r'^\s*((([0-9A-Fa-f]{1,4}:){7}([0-9A-Fa-f]{1,4}|:))|(([0-9A-Fa-f]{1,4}:){6}(:[0-9A-Fa-f]{1,4}|((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3})|:))|(([0-9A-Fa-f]{1,4}:){5}(((:[0-9A-Fa-f]{1,4}){1,2})|:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3})|:))|(([0-9A-Fa-f]{1,4}:){4}(((:[0-9A-Fa-f]{1,4}){1,3})|((:[0-9A-Fa-f]{1,4})?:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:))|(([0-9A-Fa-f]{1,4}:){3}(((:[0-9A-Fa-f]{1,4}){1,4})|((:[0-9A-Fa-f]{1,4}){0,2}:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:))|(([0-9A-Fa-f]{1,4}:){2}(((:[0-9A-Fa-f]{1,4}){1,5})|((:[0-9A-Fa-f]{1,4}){0,3}:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:))|(([0-9A-Fa-f]{1,4}:){1}(((:[0-9A-Fa-f]{1,4}){1,6})|((:[0-9A-Fa-f]{1,4}){0,4}:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:))|(:(((:[0-9A-Fa-f]{1,4}){1,7})|((:[0-9A-Fa-f]{1,4}){0,5}:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:)))(%.+)?\s*$'str_true=('2001:470:9b36:1::2','2001:cdba:0000:0000:0000:0000:3257:9652','2001:cdba:0:0:0:0:3257:9652','2001:cdba::3257:9652',)str_false=('1200::AB00:1234::2552:7777:1313',# uses `::` twice'1200:0000:AB00:1234:O000:2552:7777:1313',)# contains an O instead of 0fortinstr_true:assert(bool(re.match(pattern,t))==True),'%s is not True'%tforfinstr_false:assert(bool(re.match(pattern,f))==False),'%s is not False'%f



Checking for MAC addresses

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In [29]:
pattern=r'^(?i)([0-9A-F]{2}[:-]){5}([0-9A-F]{2})$'str_true=('94-AE-70-A0-66-83','58-f8-1a-00-44-c8','00:A0:C9:14:C8:29',)str_false=('0:00:00:00:00:00','94-AE-70-A0 -66-83',)fortinstr_true:assert(bool(re.match(pattern,t))==True),'%s is not True'%tforfinstr_false:assert(bool(re.match(pattern,f))==False),'%s is not False'%f
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