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5.17 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. Note: Because the readlines() method buffers data, this effectively ignores the effects of setting the file object as unbuffered.

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.

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Python Library Reference

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Release 2.4a0, documentation updated on 23 September 2003.