why python not supporting : while( s = f.readline())?

Question

more example below:

 if (a = xyz() ) > abc:

Really want to know why, is it kinds of bad smell ?

Note: I know the grammar, but I am asking why Python don't support such grammar as many other language( e.g., c , java...) do supporting

@MartijnPieters: That's pretty much the answer, from the either the docs or a PEP (can't remember which). — Joel Cornett, Jul 13 '12 at 07:50
possible duplicate of [Why does Python assignment not return a value?](http://stackoverflow.com/questions/4869770/why-does-python-assignment-not-return-a-value) — Martijn Pieters, Jul 13 '12 at 08:05
@JammyLee: You can 'flag' your own question, then select the 'duplicate' options (there is a menu structure to go through). A moderator will then look at it, as well as signal your post to other users with enough rep to vote to close. — Martijn Pieters, Jul 13 '12 at 09:14

score 4 · Accepted Answer · answered Jul 13 '12 at 07:56

From the python design FAQ:

The reason for not allowing assignment in Python expressions is a common, hard-to-find bug in those other languages, caused by this construct:
    if (x = 0) {
        // error handling
    }
    else {
        // code that only works for nonzero x
    }
The error is a simple typo: x = 0, which assigns 0 to the variable x, was written while the comparison x == 0 is certainly what was intended.

As explained in the FAQ, most "use cases" for using assignment in an expression can be covered by using iterators instead.

score 0 · Answer 2 · edited May 23 '17 at 12:27

0

Remember python philosophy : There should be one-- and preferably only one --obvious way to do it.
It doesn't sound obvious to me !
Also you may want to check this answer too :
why does python assignment not return a value

edited May 23 '17 at 12:27

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answered Jul 13 '12 at 08:03

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Thanks, I knew there'd be a duplicate here on SO. – Martijn Pieters Jul 13 '12 at 08:05

why python not supporting : while( s = f.readline())?

2 Answers2