syntax - What does _ in Python do? -

syntax - What does _ in Python do? -

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what purpose of single underscore “_” variable in python? 2 answers

i saw somewhere _ character beingness used in python like:

print _

can help me explain does?

in interactive interpreter, _ refers lastly outputed value:

>>> 1 + 1 2 >>> print _ 2 >>> 2 + 2 4 >>> print _ 4 >>>

in normal python1 code however, _ typical name. can assign other:

_ = 3 print _ # output: 3

although wouldn't recommend doing because _ terrible name. also, used convention mean name placeholder. illustration be:

a, _, b = [1, 2, 3]

which uses _ mean not interested in 2. illustration is:

for _ in range(10): function()

which means not using counter variable within loop. instead, want python phone call function 10 times , need _ have valid syntax.

1by "python", mean cpython, standard flavor of language. other implementations may take things differently. ipython illustration has underscore-only names:

the next global variables exist (so don’t overwrite them!):

[_] (a single underscore) : stores previous output, python’s default interpreter. [__] (two underscores): next previous. [___] (three underscores): next-next previous.

source: http://ipython.org/ipython-doc/rel-0.9.1/html/interactive/reference.html#output-caching-system

python syntax