CODEWITHSUNDEEP
python
neon
neon

Reputation: 31

File operations in Python

I have a piece of code which extracts a string that lies between two strings.However,this script performs this operation only on a line.I want to perform this operation on a complete file and get a list of all the words lying between those two words.

Note:The two words are fixed.For ex:If my code is something like 

'const int variablename=1'

then I want a list of all the words in the file lying between 'int' and '='. Here is the current script:

s='const int variablename = 1'

k=s[s.find('int')+4:s.find('=')]

print k

Upvotes: 1

Views: 1060

Answers (4)

Tim Pietzcker
Tim Pietzcker

Reputation: 336088

If the file fits comfortably into memory, you can get this with a single regex call:

import re
regex = re.compile(
r"""(?x)
(?<=    # Assert that the text before the current location is:
 \b     # word boundary
 int    # "int"
 \s     # whitespace
)       # End of lookbehind
[^=]*   # Match any number of characters except =
(?<!\s) # Assert that the previous character isn't whitespace.
(?=     # Assert that the following text is:
 \s*    # optional whitespace
 =      # "="
)       # end of lookahead""")
with open(filename) as fn:
    text = fn.read()
    matches = regex.findall(text)

If there can be only one word between int and =, then the regex is a bit more simple:

regex = re.compile(
r"""(?x)
(?<=    # Assert that the text before the current location is:
 \b     # word boundary
 int    # "int"
 \s     # whitespace
)       # End of lookbehind
[^=\s]*   # Match any number of characters except = or space
(?=     # Assert that the following text is:
 \s*    # optional whitespace
 =      # "="
)       # end of lookahead""")

Upvotes: 3

moliware
moliware

Reputation: 10278

I would use regular expressions over whole text (you can do it over one line too). This prints strings betweet "int " and "="

import re

text = open('example.txt').read()
print re.findall('(?<=int\s).*?(?=\=)', text)

Upvotes: 1

ykatchou
ykatchou

Reputation: 3727

If you want a quick and dirty ways and you're on a unix-like system.

I just should use a grep on the file. Then i will split the string in order to recognize the pattern and the data i want.

Upvotes: 0

Vito De Tullio
Vito De Tullio

Reputation: 2121

with open(filename) as fn:
    for row in fn:
        # do something with the row?

Upvotes: 2

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