5.12 `xreadlines` -- Efficient iteration over a file

New in version 2.1.

This module defines a new object type which can efficiently iterate over the lines of a file. An xreadlines object is a sequence type which implements simple in-order indexing beginning at 0, as required by for statement or the filter() function.

Thus, the code

import xreadlines, sys

for line in xreadlines.xreadlines(sys.stdin):
    pass

has approximately the same speed and memory consumption as

while 1:
    lines = sys.stdin.readlines(8*1024)
    if not lines: break
    for line in lines:
        pass

except the clarity of the for statement is retained in the former case.

xreadlines(fileobj): Return a new xreadlines object which will iterate over the contents of fileobj. fileobj must have a readlines() method that supports the sizehint parameter.

An xreadlines object s supports the following sequence operation:

Operation Result

s[i] i'th line of s

If successive values of i are not sequential starting from 0, this code will raise RuntimeError.

After the last line of the file is read, this code will raise an IndexError.

See About this document... for information on suggesting changes.

5.12 xreadlines -- Efficient iteration over a file

5.12 `xreadlines` -- Efficient iteration over a file