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How totell a binary file from a nonbinary file.

Phil Austin phil at geog.ubc.ca
Sun Oct 29 12:58:20 EST 2000 
olczyk at interaccess.com (Thaddeus L. Olczyk) writes:

> There are some changes that I have to make to s directory of files (
> in python of course ). Is there some simple way of telling whether 
> a file is binary or not (from python of course )? 

Something like this might help:

#
# Detects if files contain text or binary data
# Jeff Epler  jepler at inetnebr.com  20 April 97
#
import string
import os

def mask(charlist):
        """Construct a mask suitable for string.translate,
        which marks letters in charlist as "t" and ones not as "b" """
        mask=""
        for i in range(256):
                if chr(i) in charlist: mask=mask+"t"
                else: mask=mask+"b"
        return mask

ascii7bit=string.joinfields(map(chr, range(32,127)), "")+"\r\n\t\b"
ascii7bit_mask=mask(ascii7bit)

def istext(file, check=1024, mask=ascii7bit_mask):
        """Returns true if the first check characters in file
        are within mask, false otherwise"""

        try:
                s=file.read(check)
                s=string.translate(s, mask)
                if string.find(s, "b") != -1: return 0
                return 1
        except (AttributeError, NameError): # Other exceptions?
                return istext(open(file, "r"))

def main(argv):
        for filename in argv:
                print filename+":",
		if os.path.isfile(filename):
	                if istext(filename): print "text"
        	        else: print "binary"
		elif os.path.isdir(filename):
			print "directory"
		else: print "not file or directory"

if __name__=='__main__':
        import sys
        main(sys.argv[1:])
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