iter(lambda:f.read(8192),'')

Dustan DustanGroups at gmail.com
Sun Feb 24 13:18:31 CET 2008


On Feb 24, 5:11 am, gert <gert.cuyk... at gmail.com> wrote:
> what is the difference between iter(lambda:f.read(8192), ') and
> iter(f.read(8192),'') ?

One does not work, and one is syntactically incorrect:

>>> iter(f.read(8192),'')

Traceback (most recent call last):
  File "<pyshell#0>", line 1, in <module>
    iter(f.read(8192),'')
TypeError: iter(v, w): v must be callable
>>> iter(lambda:f.read(8192), ')

SyntaxError: EOL while scanning single-quoted string

To clarify:

f.read(8192) returns the next 8192 bytes of the file in a string, or
whatever is leftover, or an empty string when the file is exhausted.
lambda: f.read(8192) is a function that will return the next 8192
bytes of the file every time it is called.

So iter(f.read(8192),'') is evaluated as iter(some_string, ''). When
iter receives two arguments, it expects the first to be a function,
not a string.

iter(lambda:f.read(8192), '') (what you probably meant) is what it
looks like: iter(some_func, '').



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