For Loop Structure in Python

Question

Is it possible to have the following logic of a for loop in python?:

with  open("file_r", "r") as infile, open("file_1", 'w') as outfile_1, open("file_2", 'w') as outfile_2: 
    for result in re.findall('somestring(.*?)\}', infile.read(), re.S):
       for line in result.split('\n'):
           outfile_1.write(line) 

    for result in re.findall('sime_other_string(.*?)\}', infile.read(), re.S):
       for line in result.split('\n'):
           outfile_2.write(line)

I'm asking because the result of the first foor loop are written to the "outfile_1" file, but the results of the secund loop are empty in the "outfile_2" file.

arocks · Accepted Answer · 2014-02-19 09:41:06Z

3

Save infile.read() into a variable else the file will be finished in the first loop itself. Say:

with  open("file_r", "r") as infile, open("file_1", 'w') as outfile_1, open("file_2", 'w') as outfile_2: 
    contents = infile.read()

    for result in re.findall('somestring(.*?)\}', contents, re.S):
       for line in result.split('\n'):
           outfile_1.write(line) 

    for result in re.findall('sime_other_string(.*?)\}', contents, re.S):
       for line in result.split('\n'):
           outfile_2.write(line)

answered Feb 19, 2014 at 9:41

arocks

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2 Comments

Jayanth Koushik Over a year ago

And you could use comprehension to simplify the two loops.

user3296561 Over a year ago

Ouh! Thx a lot!! It works now with saving infile.read() to a variable!

Martijn Pieters · Accepted Answer · 2014-02-19 09:40:54Z

0

Only if you 'rewind' infile to the start again in between reads:

... infile.read()

infile.seek(0)

... infile.read()

A file is a lot like an audiotape; when you read a reading 'head' moves along the tape and returns the data. file.seek() moves the reading 'head' to a different position, infile.seek(0) moves it to the start again.

You'd be better off reading the file just once though:

content_of_infile = infile.read()

for result in re.findall('somestring(.*?)\}', content_of_infile, re.S):
    # ...

for result in re.findall('sime_other_string(.*?)\}', contents_of_infile, re.S):
    # ...

answered Feb 19, 2014 at 9:40

Martijn Pieters

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