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July 24, 2008 01:41pm pdt
 
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python while loop question

Tags: python, firefox
I'm trying to have python read in a file and put each line into a list, then print out each list, but stop at a command line argument supplied number

so file is 30 lines long, argument is 20, i want it to just print out 20 lines. but its printing all 30 lines out. I'm a python newbie

am i just writing this wrong?
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import sys
import getopt
    
if __name__ == "__main__":
    args = sys.argv[1]
    print args
    f = open("file1.txt")
    count = 0
    l = f.readlines()
    while count<20:
        for line in l:
            print line
            count = count + 1
    print count
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Question Stats
Zone: Programming
Question Asked By: superwick
Solution Provided By: pepr
Participating Experts: 2
Solution Grade: A
Views: 94
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[+][-]Expert Comment by ghostdog74
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Comment by pepr
I agree with ghostdog74 modification. Using the enumerate function simplifies the code and makes it cleaner. I only suggest to use a different identifier for the line as lower-case L can be mistaken with one. Also the opened file object should be given a name (i.e. the accessor to the file object) because it is not possible to close the file explicitly otherwise.

The head() generator then can be written this way...
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def head(fname, maxcount):
    '''Generator returning maxcount lines from the fname.'''
 
    f = open(fname)         # Generator started. Open the file.
    for count, line in enumerate(f):
        if count >= maxcount:
            break
        yield line          # Generate the value.
    f.close()               # Generator stopped. Close the file.
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