Reading Files

CS 233 Python Lecture Examples

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#!/usr/bin/python

# Print the contents of the files listed on the command line.

import sys

for fn in sys.argv[1:]:
    try:
        fin = open(fn, 'r')
    except:
        (type, detail) = sys.exc_info()[:2]
        print "\n*** %s: %s: %s ***" % (fn, type, detail)
        continue
    print "\n*** Contents of", fn, "***"
    
    # Print the file, with line numbers.
    lno = 1
    while 1:
        line = fin.readline()
        if not line: break;
        print '%3d: %-s' % (lno, line[:-1])
        lno = lno + 1
    fin.close()
print

This program simply takes a list of files on the command line, and lists the contents of each, with lines numbered.

There are a couple of new things from sys used here.

sys.argv: This gives the list of command line arguments. The first one (position zero) is the name of the script, as in C.
sys.exc_info: This returns a list of information about the current exception. The first item is the name of the exception, the second is the detail information, and the third is the call stack trace-back.