how to avoid buffering in the python fileinput library

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What worked for me was simply setting FileInput(bufsize=1). The file.readlines() documentation does state "The optional size argument, if given, is an approximate bound on the total number of bytes in the lines returned." In practice, I get exactly one new line every time rather than having to fill a buffer.

with fileinput.input(bufsize = 1) as f:
   for line in f:
   print("One line in, one line out!")

Suggestion : 2

This module implements a helper class and functions to quickly write a loop over standard input or a list of files. If you just want to read or write one file see open().,Create an instance of the FileInput class. The instance will be used as global state for the functions of this module, and is also returned to use during iteration. The parameters to this function will be passed along to the constructor of the FileInput class.,The openhook, when given, must be a function that takes two arguments, filename and mode, and returns an accordingly opened file-like object. You cannot use inplace and openhook together.,This iterates over the lines of all files listed in sys.argv[1:], defaulting to sys.stdin if the list is empty. If a filename is '-', it is also replaced by sys.stdin and the optional arguments mode and openhook are ignored. To specify an alternative list of filenames, pass it as the first argument to input(). A single file name is also allowed.

import fileinput
for line in fileinput.input(encoding = "utf-8"):
with fileinput.input(files = ('spam.txt', 'eggs.txt'), encoding = "utf-8") as f:
   for line in f:
with FileInput(files = ('spam.txt', 'eggs.txt')) as input:

Suggestion : 3

This issue tracker has been migrated to GitHub, and is currently read-only. For more information, see the GitHub FAQs in the Python's Developer Guide.

for line in fileinput.input(files, inplace, backup, "rU"):
   File "/usr/lib/python2.7/", line 253, in next
line = self.readline()
File "/usr/lib/python2.7/", line 346, in readline
self._buffer = self._file.readlines(self._bufsize)
TypeError: an integer is required

According to the documentation, my code was correct.But somewhere along the line, someone added a 'bufsize'
parameter and didn 't update the docstrings.

It 's an easy fix, but I'
ll have to investigate when this broke.
http: //

   In the process, I added an optional bufsize argument to the input() >
   function and the FileInput class.
A quick look at the VCS history indicates bufsize has been in there
for a long time.The sphinx docs are wrong as well.This is correctly documented in python3, apparently as part of the conversion from[] notation to keyword notation in d143eb624cf5.
http: //

   This is where the incorrect docstrings get added.
Here is a patch against the 2.7 branch.It will probably also apply to 2.6
if anyone cares.
Oops.I messed up, even on such a tiny fix.#: (

Suggestion : 4

Python - Basic Syntax


print "Python is really a great language,", "isn't it?"

This produces the following result on your standard screen −

Python is really a great language, isn 't it?

The raw_input([prompt]) function reads one line from standard input and returns it as a string (removing the trailing newline).


str = raw_input("Enter your input: ")
print "Received input is : ", str

The input([prompt]) function is equivalent to raw_input, except that it assumes the input is a valid Python expression and returns the evaluated result to you.


str = input("Enter your input: ")
print "Received input is : ", str

This would produce the following result against the entered input −

Enter your input: [x * 5
   for x in range(2, 10, 2)
Recieved input is: [10, 20, 30, 40]

Suggestion : 5

Last Updated : 22 Jun, 2022