Is it safe to rely on Python function arguments evaluation order? [duplicate]

Quoting from the reference documentation:

Python evaluates expressions from left to right.

So yes, you can count on that (with one exception, see below).

A call (the (...) part after a primary, such as a function name) is just another expression primary, and the arguments for the call are just more expressions.

Note: There is one exception to this rule. When using *expression in a call (to expand an iterable to form additional positional arguments), then this expression is evaluated before any keyword argument expressions:

>>> from itertools import count>>> def bar(n, r=(), c=count()): print(f'{next(c)}: bar({n!r})'); return r...>>> def foo(*args, **kwargs): pass...>>> foo(bar('a1'), spam=bar('a2'), *bar('varargs'), **bar('kwargs', {}))0: bar('a1')1: bar('varargs')2: bar('a2')3: bar('kwargs')

The linked documentation states:

A consequence of this is that although the *expression syntax may appear after explicit keyword arguments, it is processed before the keyword arguments[.]

Yes, Python always evaluates function arguments from left to right.

This goes for any comma seperated list as far as I know:

>>> from __future__ import print_function>>> def f(x, y): pass...>>> f(print(1), print(2))12>>> [print(1), print(2)]12[None, None]>>> {1:print(1), 2:print(2)}12{1: None, 2: None}>>> def f(x=print(1), y=print(2)): pass...12