adii1823
59 lines
1.3 KiB
Python
59 lines
1.3 KiB
Python
# parameters.positional.only.py
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def func(a, b, /, c):
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print(a, b, c)
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func(1, 2, 3) # prints: 1 2 3
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func(1, 2, c=3) # prints 1 2 3
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# func(1, b=2, c=3) # produces the following traceback:
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"""
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Traceback (most recent call last):
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File "arguments.positional.only.py", line 7, in <module>
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func(1, b=2, c=3)
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TypeError: func() got some positional-only arguments
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passed as keyword arguments: 'b'
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"""
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"""
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def func_name(positional_only_parameters, /,
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positional_or_keyword_parameters, *,
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keyword_only_parameters):
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Valid:
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def func_name(p1, p2, /, p_or_kw, *, kw):
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def func_name(p1, p2=None, /, p_or_kw=None, *, kw):
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def func_name(p1, p2=None, /, *, kw):
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def func_name(p1, p2=None, /):
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def func_name(p1, p2, /, p_or_kw):
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def func_name(p1, p2, /):
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Invalid:
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def func_name(p1, p2=None, /, p_or_kw, *, kw):
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def func_name(p1=None, p2, /, p_or_kw=None, *, kw):
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def func_name(p1=None, p2, /):
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Why it is useful:
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def divmod(a, b, /):
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"Emulate the built in divmod() function"
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return (a // b, a % b)
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len(obj='hello') # The "obj" keyword argument impairs readability
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"""
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def func_name(name, /, **kwargs):
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print(name)
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print(kwargs)
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func_name('Positional-only name', name='Name in **kwargs')
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"""
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Prints:
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Positional-only name
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{'name': 'Name in **kwargs'}
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"""
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