The fileinput
module allows you to loop over the contents of one or more text
files, as shown in Example 2-1.
Example 2-1. Using the fileinput Module to Loop Over a Text File
File: fileinput-example-1.py import fileinput import sys for line in fileinput.input("samples/sample.txt"): sys.stdout.write("-> ") sys.stdout.write(line)-> We will perhaps eventually be writing only small
-> modules which are identified by name as they are
-> used to build larger ones, so that devices like
-> indentation, rather than delimiters, might become
-> feasible for expressing local structure in the
-> source language.
-> -- Donald E. Knuth, December 1974
The fileinput
module also allows you to get metainformation about the current
line. This includes isfirstline
,
filename
, and lineno
, as Example 2-2 shows.
Example 2-2. Using the fileinput Module to Process Multiple Files
File: fileinput-example-2.py import fileinput import glob import string, sys for line in fileinput.input(glob.glob("samples/*.txt")): if fileinput.isfirstline(): # first in a file? sys.stderr.write("-- reading %s -- " % fileinput.filename()) sys.stdout.write(str(fileinput.lineno()) + " " + string.upper(line))-- reading samplessample.txt --
1 WE WILL PERHAPS EVENTUALLY BE WRITING ONLY SMALL
2 MODULES WHICH ARE IDENTIFIED BY NAME AS THEY ARE
3 USED TO BUILD LARGER ONES, SO THAT DEVICES LIKE
4 INDENTATION, RATHER THAN DELIMITERS, MIGHT BECOME
5 FEASIBLE FOR EXPRESSING LOCAL STRUCTURE IN THE
6 SOURCE LANGUAGE.
7 -- DONALD E. KNUTH, DECEMBER 1974
Processing text files in place is also easy. Just call the
input
function with the
inplace
keyword argument set to 1, and the module
takes care of the rest. Example 2-3 demonstrates this.
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