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Is it possible to declare more than one variable using a with statement in Python?
Something like:
from __future__ import with_statement with open("out.txt","wt"), open("in.txt") as file_out, file_in: for line in file_in: file_out.write(line) ... or is cleaning up two resources at the same time the problem?
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First, use a SWITCH(TRUE()...) statement instead of nested IF statements. Far cleaner, more readable and easier to modify. Second, use the logical operators && (AND) and || (OR) to combine multiple criteria.
Yes, I can declare multiple variables in a for-loop. And you, too, can now declare multiple variables, in a for-loop, as follows: Just separate the multiple variables in the initialization statement with commas. Do not forget to end the complete initialization statement with a semicolon.
Because Python's original parser is LL(1), it cannot distinguish between "multiple context managers" with (A(), B()): and "tuple of values" with (A(), B())[0]: . The new parser can properly parse multiple context managers surrounded by parentheses.
No, you cannot. You cannot use augmented assignment together with multiple targets.
It is possible in Python 3 since v3.1 and Python 2.7. The new with syntax supports multiple context managers:
with A() as a, B() as b, C() as c: doSomething(a,b,c) Unlike the contextlib.nested, this guarantees that a and b will have their __exit__()'s called even if C() or it's __enter__() method raises an exception.
You can also use earlier variables in later definitions (h/t Ahmad below):
with A() as a, B(a) as b, C(a, b) as c: doSomething(a, c) As of Python 3.10, you can use parentheses:
with ( A() as a, B(a) as b, C(a, b) as c, ): doSomething(a, c) If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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