Develop Reference

How do I print matches from a regex given a string value in Python?

I have the string "/browse/advanced-computer-science-modules?title=machine-learning"** in Python. I want to print the string in between the second "/" and the "?", which is "advanced-computer-science-modules".
I've created a regular expression that is as follows ^([a-z]*[\-]*[a-z])*?$ but it prints nothing when I run the .findall() function from the re module.
I created my own regex and imported the re module in python. Below is a snippet of my code that returned nothing.
regex = re.compile(r'^([a-z]*[\-]*[a-z])*?$')
str = '/browse/advanced-computer-science-modules?title=machine-learning'
print(regex.findall(str))

Since this appears to be a URL, I'd suggest you use URL-parsing tools instead:
>>> from urllib.parse import urlsplit
>>> url = '/browse/advanced-computer-science-modules?title=machine-learning'
>>> s = urlsplit(url)
SplitResult(scheme='', netloc='', path='/browse/advanced-computer-science-modules', query='title=machine-learning', fragment='')
>>> s.path
'/browse/advanced-computer-science-modules'
>>> s.path.split('/')[-1]
'advanced-computer-science-modules'

The regex is as follows:
\/[a-zA-Z\-]+\?
Then you catch the substring:
regex.findall(str)[1:len(str) - 1]
Very specific to this problem, but it should work.

Alternatively, you can use split method of a string:
str = '/browse/advanced-computer-science-modules?title=machine-learning'
result = str.split('/')[-1].split('?')[0]
print(result)
#advanced-computer-science-modules

python 3 remove before and after on string

I have this string /1B5DB40?full and I want to convert it to 1B5DB40.
I need to remove the ?full and the front /
My site won't always have ?full at the end so I need something that will still work even if the ?full is not there.
Thanks and hopefully this isn't too confusing to get some help :)
EDIT:
I know I could slice at 0 and 8 or whatever, but the 1B5DB40 could be longer or shorter. For example it could be /1B5DB4000?full or /1B5

Using str.lstrip (to remove leading /) and str.split (to remove optinal part after ?):
>>> '/1B5DB40?full'.lstrip('/').split('?')[0]
'1B5DB40'
>>> '/1B5DB40'.lstrip('/').split('?')[0]
'1B5DB40'
or using urllib.parse.urlparse:
>>> import urllib.parse
>>> urllib.parse.urlparse('/1B5DB40?full').path.lstrip('/')
'1B5DB40'
>>> urllib.parse.urlparse('/1B5DB40').path.lstrip('/')
'1B5DB40'

You can use lstrip and rstrip:
>>> data.lstrip('/').rstrip('?full')
'1B5DB40'
This only works as long as you don't have the characters f, u, l, ?, / in the part that you want to extract.

You can use regular expressions:
>>> import re
>>> extract = re.compile('/?(.*?)\?full')
>>> print extract.search('/1B5DB40?full').group(1)
1B5DB40
>>> print extract.search('/1Buuuuu?full').group(1)
1Buuuuu

What about regular expressions?
import re
re.search(r'/(?P<your_site>[^\?]+)', '/1B5DB40?full').group('your_site')
In this case it matches everything that is between '/' and '?', but you can change it to your specific requirements

>>> '/1B5DB40?full'split('/')[1].split('?')[0]
'1B5DB40'
>>> '/1B5'split('/')[1].split('?')[0]
'1B5'
>>> '/1B5DB40000?full'split('/')[1].split('?')[0]
'1B5DB40000'
Split will simply return a single element list containing the original string if the separator is not found.

Using regular expression to extract string

I need to extract the IP address from the following string.
>>> mydns='ec2-54-196-170-182.compute-1.amazonaws.com'
The text to the left of the dot needs to be returned. The following works as expected.
>>> mydns[:18]
'ec2-54-196-170-182'
But it does not work in all cases. For e.g.
mydns='ec2-666-777-888-999.compute-1.amazonaws.com'
>>> mydns[:18]
'ec2-666-777-888-99'
How to I use regular expressions in python?

No need for regex... Just use str.split
mydns.split('.', 1)[0]
Demo:
>>> mydns='ec2-666-777-888-999.compute-1.amazonaws.com'
>>> mydns.split('.', 1)[0]
'ec2-666-777-888-999'

If you wanted to use regex for this:
Regex String
ec2-([0-9]{1,3})-([0-9]{1,3})-([0-9]{1,3})-([0-9]{1,3}).*
Alternative (EC2 Agnostic):
.*\b([0-9]{1,3})-([0-9]{1,3})-([0-9]{1,3})-([0-9]{1,3}).*
Replacement String
Regular: \1.\2.\3.\4
Reverse: \4.\3.\2.\1
Python code
import re
subject = 'ec2-54-196-170-182.compute-1.amazonaws.com'
result = re.sub("ec2-([0-9]{1,3})-([0-9]{1,3})-([0-9]{1,3})-([0-9]{1,3}).*", r"\1.\2.\3.\4", subject)
print result

This regex will match (^[^.]+:
So Try this:
import re
string = "ec2-54-196-170-182.compute-1.amazonaws.com"
ip = re.findall('^[^.]+',string)[0]
print ip
Output:
ec2-54-196-170-182
Best thing is this will match even if the instance was ec2,ec3 so this regex is actually very much similar to the code of #mgilson

Python - Extract important string information

I have the following string
http://example.com/variable/controller/id32434242423423234?param1=321&param2=4324342
How in best way to extract id value, in this case - 32434242423423234
Regardz,
Mladjo

You could just use a regular expression, e.g.:
import re
s = "http://example.com/variable/controller/id32434242423423234?param1=321&param2=4324342"
m = re.search(r'controller/id(\d+)\?',s)
if m:
print "Found the id:", m.group(1)
If you need the value as an number rather than a string, you can use int(m.group(1)). There are plenty of other ways of doing this that might be more appropriate, depending on the larger goal of your code, but without more context it's hard to say.

>>> import urlparse
>>> res=urlparse.urlparse("http://example.com/variable/controller/id32434242423423234?param1=321&param2=4324342")
>>> res.path
'/variable/controller/id32434242423423234'
>>> import posixpath
>>> posixpath.split(res.path)
('/variable/controller', 'id32434242423423234')
>>> directory,filename=posixpath.split(res.path)
>>> filename[2:]
'32434242423423234'
Using urlparse and posixpath might be too much for this case, but I think it is the clean way to do it.

>>> s
'http://example.com/variable/controller/id32434242423423234?param1=321&param2=4324342'
>>> s.split("id")
['http://example.com/variable/controller/', '32434242423423234?param1=321&param2=4324342']
>>> s.split("id")[-1].split("?")[0]
'32434242423423234'
>>>

While Regex is THE way to go, for simple things I have written a string parser. In a way, is the (uncomplete) reverse operation of a string formatting operation with PEP 3101. This is very convenient because it means that you do not have to learn another way of specifying the strings.
For example:
>>> 'The answer is {:d}'.format(42)
The answer is 42
The parser does the opposite:
>>> Parser('The answer is {:d}')('The answer is 42')
42
For your case, if you want an int as output
>>> url = 'http://example.com/variable/controller/id32434242423423234?param1=321&param2=4324342'
>>> fmt = 'http://example.com/variable/controller/id{:d}?param1=321&param2=4324342'
>>> Parser(fmt)(url)
32434242423423234
If you want a string:
>>> fmt = 'http://example.com/variable/controller/id{:s}?param1=321&param2=4324342'
>>> Parser(fmt)(url)
32434242423423234
If you want to capture more things in a dict:
>>> fmt = 'http://example.com/variable/controller/id{id:s}?param1={param1:s}&param2={param2:s}'
>>> Parser(fmt)(url)
{'id': '32434242423423234', 'param1': '321', 'param2': '4324342'}
or in a tuple:
If you want to capture more things in a dict:
>>> fmt = 'http://example.com/variable/controller/id{:s}?param1={:s}&param2={:s}'
>>> Parser(fmt)(url)
('32434242423423234', '321', '4324342')
Give it a try, it is hosted here

How to split a string by using [] in Python

So from this string:
"name[id]"
I need this:
"id"
I used str.split ('[]'), but it didn't work. Does it only take a single delimiter?

Use a regular expression:
import re
s = "name[id]"
re.find(r"\[(.*?)\]", s).group(1) # = 'id'
str.split() takes a string on which to split input. For instance:
"i,split,on commas".split(',') # = ['i', 'split', 'on commas']
The re module also allows you to split by regular expression, which can be very useful, and I think is what you meant to do.
import re
s = "name[id]"
# split by either a '[' or a ']'
re.split('\[|\]', s) # = ['name', 'id', '']

Either
"name[id]".split('[')[1][:-1] == "id"
or
"name[id]".split('[')[1].split(']')[0] == "id"
or
re.search(r'\[(.*?)\]',"name[id]").group(1) == "id"
or
re.split(r'[\[\]]',"name[id]")[1] == "id"

Yes, the delimiter is the whole string argument passed to split. So your example would only split a string like 'name[]id[]'.
Try eg. something like:
'name[id]'.split('[', 1)[-1].split(']', 1)[0]
'name[id]'.split('[', 1)[-1].rstrip(']')

I'm not a fan of regex, but in cases like it often provides the best solution.
Triptych already recommended this, but I'd like to point out that the ?P<> group assignment can be used to assign a match to a dictionary key:
>>> m = re.match(r'.*\[(?P<id>\w+)\]', 'name[id]')
>>> result_dict = m.groupdict()
>>> result_dict
{'id': 'id'}
>>>

You don't actually need regular expressions for this. The .index() function and string slicing will work fine.
Say we have:
>>> s = 'name[id]'
Then:
>>> s[s.index('[')+1:s.index(']')]
'id'
To me, this is easy to read: "start one character after the [ and finish before the ]".

def between_brackets(text):
return text.partition('[')[2].partition(']')[0]
This will also work even if your string does not contain a […] construct, and it assumes an implied ] at the end in the case you have only a [ somewhere in the string.

I'm new to python and this is an old question, but maybe this?
str.split('[')[1].strip(']')

You can get the value of the list use []. For example, create a list from URL like below with split.
>>> urls = 'http://quotes.toscrape.com/page/1/'
This generates a list like the one below.
>>> print( urls.split("/") )
['http:', '', 'quotes.toscrape.com', 'page', '11', '']
And what if you wanna get value only "http" from this list? You can use like this
>>> print(urls.split("/")[0])
http:
Or what if you wanna get value only "1" from this list? You can use like this
>>> print(urls.split("/")[-2])
1

str.split uses the entire parameter to split a string. Try:
str.split("[")[1].split("]")[0]