Forced keyword-only parameters in Python 3.x

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April 27, 2018 Python No Comments

# In Python 3 you can use a bare “*” asterisk
# in function parameter lists to force the
# caller to use keyword arguments for certain
# parameters:

>>> def f(a, b, *, c=’x’, d=’y’, e=’z’):
… return ‘Hello’

# To pass the value for c, d, and e you
# will need to explicitly pass it as
# “key=value” named arguments:
>>> f(1, 2, ‘p’, ‘q’, ‘v’)
TypeError:
“f() takes 2 positional arguments but 5 were given”

>>> f(1, 2, c=’p’, d=’q’,e=’v’)
‘Hello’

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