Develop Reference

How to replace an re match with a transformation of that match?

For example, I have a string:
The struct-of-application and struct-of-world
With re.sub, it will replace the matched with a predefined string. How can I replace the match with a transformation of the matched content? To get, for example:
The [application_of_struct](http://application_of_struct) and [world-of-struct](http://world-of-struct)
If I write a simple regex ((\w+-)+\w+) and try to use re.sub, it seems I can't use what I matched as part of the replacement, let alone edit the matched content:
In [10]: p.sub('struct','The struct-of-application and struct-of-world')
Out[10]: 'The struct and struct'

Use a function for the replacement
s = 'The struct-of-application and struct-of-world'
p = re.compile('((\w+-)+\w+)')
def replace(match):
return 'http://{}'.format(match.group())
#for python 3.6+ ...
#return f'http://{match.group()}'
>>> p.sub(replace, s)
'The http://struct-of-application and http://struct-of-world'
>>>

Try this:
>>> p = re.compile(r"((\w+-)+\w+)")
>>> p.sub('[\\1](http://\\1)','The struct-of-application and struct-of-world')
'The [struct-of-application](http://struct-of-application) and [struct-of-world](http://struct-of-world)'

Split string multiple times in Python

This should be a simple thing to do but I can't get it to work.
Say I have this string.
I want this string to be splitted into smaller strings.
And, well, I want to split it into smaller strings, but only take what is between a T and a S.
So, the result should yield
this, to be s, to s, trings
So far I've tried splitting on every S, and then up to every T (backwards). However, it will only get the first "this", and stop. How can I make it continue and get all the things that are between T's and S's?
(In this program I export the results to another text file)
matches = open('string.txt', 'r')
with open ('test.txt', 'a') as file:
for line in matches:
test = line.split("S")
file.write(test[0].split("T")[-1] + "\n")
matches.close()
Maybe using Regular Expressions would be better, though I don't know how to work with them too well?

You want a re.findall() call instead:
re.findall(r't[^s]*s', line, flags=re.I)
Demo:
>>> import re
>>> sample = 'I want this string to be splitted into smaller strings.'
>>> re.findall(r't[^s]*s', sample, flags=re.I)
['t this', 'tring to be s', 'tted into s', 'trings']
Note that this matches 't this' and 'tted into s'; your rules need clarification as to why those first t characters shouldn't match when 'trings' does.
It sounds as if you want to match only text between t and s without including any other t:
>>> re.findall(r't[^ts]*s', sample, flags=re.I)
['this', 'to be s', 'to s', 'trings']
where tring in the second result and tted in the 3rd are not included because there is a later t in those results.

splitting merged words in python

I am working with a text where all "\n"s have been deleted (which merges two words into one, like "I like bananasAnd this is a new line.And another one.") What I would like to do now is tell Python to look for combinations of a small letter followed by capital letter/punctuation followed by capital letter and insert a whitespace.
I thought this would be easy with reg. expressions, but it is not - I couldnt find an "insert" function or anything, and the string commands seem not to be helpful either. How do I do this?
Any help would be greatly appreciated, I am despairing over here...
Thanks, patrick

Try the following:
re.sub(r"([a-z\.!?])([A-Z])", r"\1 \2", your_string)
For example:
import re
lines = "I like bananasAnd this is a new line.And another one."
print re.sub(r"([a-z\.!?])([A-Z])", r"\1 \2", lines)
# I like bananas And this is a new line. And another one.
If you want to insert a newline instead of a space, change the replacement to r"\1\n\2".

Using re.sub you should be able to make a pattern that grabs a lowercase and uppercase letter and substitutes them for the same two letters, but with a space in between:
import re
re.sub(r'([a-z][.?]?)([A-Z])', '\\1\n\\2', mystring)

You're looking for the sub function. See http://docs.python.org/library/re.html for documentation.

Hmm, interesting. You can use regular expressions to replace text with the sub() function:
>>> import re
>>> string = 'fooBar'
>>> re.sub(r'([a-z][.!?]*)([A-Z])', r'\1 \2', string)
'foo Bar'

If you really don't have any caps except at the beginning of a sentence, it will probably be easiest to just loop through the string.
>>> import string
>>> s = "a word endsA new sentence"
>>> lastend = 0
>>> sentences = list()
>>> for i in range(0, len(s)):
... if s[i] in string.uppercase:
... sentences.append(s[lastend:i])
... lastend = i
>>> sentences.append(s[lastend:])
>>> print sentences
['a word ends', 'A new sentence']

Here's another approach, which avoids regular expressions and does not use any imported libraries, just built-ins...
s = "I like bananasAnd this is a new line.And another one."
with_whitespace = ''
last_was_upper = True
for c in s:
if c.isupper():
if not last_was_upper:
with_whitespace += ' '
last_was_upper = True
else:
last_was_upper = False
with_whitespace += c
print with_whitespace
Yields:
I like bananas And this is a new line. And another one.

Replace ",**" with a linebreak using RegEx (or something else)

I'm getting started with RegEx and I was wondering if anyone could help me craft a statement to convert coordinates as follows:
145.00694,-37.80421,9 145.00686,-37.80382,9 145.00595,-37.8035,16 145.00586,-37.80301,16
to
145.00694,-37.80421
145.00686,-37.80382
145.00595,-37.8035
145.00586,-37.80301
(Strip off the last comma and value and turn it into a line break.)
I can't figure out how to use wildcards to do something like that. Any help would be greatly appreciated! Thanks.

"Some people, when confronted with a
problem, think 'I know, I'll use
regular expressions.' Now they have
two problems." --Jamie Zawinski
Avoid that problem and use string methods:
s="145.00694,-37.80421,9 145.00686,-37.80382,9 145.00595,-37.8035,16 145.00586,37.80301,16"
lines = s.split(' ') # each line is separated by ' '
for line in lines:
a,b,c=line.split(',') # three parts, separated by ','
print a,b
Regex have their uses, but this is not one of them.

>>> import re
>>> s="145.00694,-37.80421,9 145.00686,-37.80382,9 145.00595,-37.8035,16 145.00586,-37.80301,16"
>>> print re.sub(",\d*\w","\n",s)
145.00694,-37.80421
145.00686,-37.80382
145.00595,-37.8035
145.00586,-37.80301

String methods seem to suffice here, regex are overkill:
>>> s='145.00694,-37.80421,9 145.00686,-37.80382,9 145.00595,-37.8035,16 145.00586,-37.80301,16'
>>> print('\n'.join(line.rpartition(',')[0] for line in s.split()))
145.00694,-37.80421
145.00686,-37.80382
145.00595,-37.8035
145.00586,-37.80301

>>> s = '145.00694,37.80421,9 145.00686,-37.80382,9 145.00595,-37.8035,16 145.00586,-37.80301,16
>>> patt = '(%s,%s),%s' % (('[+-]?\d+\.?\d*', )*3)
>>> m = re.findall(patt, s)
>>> m
['145.00694,37.80421', '145.00686,-37.80382', '145.00595,-37.8035', '145.00586,-37.80301']
>>> print '\n'.join(m)
145.00694,37.80421
145.00686,-37.80382
145.00595,-37.8035
145.00586,-37.80301
but I prefer not use regular expressions in this case
I like SilentGhost solution

Create a Reg Exp to search for __word__?

In a program I'm making in python and I want all words formatted like __word__ to stand out. How could I search for words like these using a regex?

Perhaps something like
\b__(\S+)__\b
>>> import re
>>> re.findall(r"\b__(\S+)__\b","Here __is__ a __test__ sentence")
['is', 'test']
>>> re.findall(r"\b__(\S+)__\b","__Here__ is a test __sentence__")
['Here', 'sentence']
>>> re.findall(r"\b__(\S+)__\b","__Here's__ a test __sentence__")
["Here's", 'sentence']
or you can put tags around the word like this
>>> print re.sub(r"\b(__)(\S+)(__)\b",r"<b>\2<\\b>","__Here__ is a test __sentence__")
<b>Here<\b> is a test <b>sentence<\b>
If you need more fine grained control over the legal word characters it's best to be explicit
\b__([a-zA-Z0-9_':])__\b ### count "'" and ":" as part of words
>>> re.findall(r"\b__([a-zA-Z0-9_']+)__\b","__Here's__ a test __sentence:__")
["Here's"]
>>> re.findall(r"\b__([a-zA-Z0-9_':]+)__\b","__Here's__ a test __sentence:__")
["Here's", 'sentence:']

Take a squizz here: http://docs.python.org/library/re.html
That should show you syntax and examples from which you can build a check for word(s) pre- and post-pended with 2 underscores.

The simplest regex for this would be
__.+__
If you want access to the word itself from your code, you should use
__(.+)__

This will give you a list with all such words
>>> import re
>>> m = re.findall("(__\w+__)", "What __word__ you search __for__")
>>> print m
['__word__', '__for__']

\b(__\w+__)\b
\b word boundary
\w+ one or more word characters - [a-zA-Z0-9_]

simple string functions. no regex
>>> mystring="blah __word__ blah __word2__"
>>> for item in mystring.split():
... if item.startswith("__") and item.endswith("__"):
... print item
...
__word__
__word2__