*Memo:
- My post explains a function.
- My post explains parameters and arguments in a function.
- My post explains keyword-only parameters in a function.
- My post explains positional-only parameters and keyword-only parameters together in a function.
Positional-only parameters can be set to a function definition as shown below:
*Memo:
- A positional-only parameter is the parameter which only accepts a positional argument.
- All the parameters before
/are positional-only parameters. - Positional-only parameters are added from Python 3.8.
<Required parameters>:
def func(fname, lname, /, age, gender): pass def func(fname, lname, age, gender, /): pass # No error def func(fname, /, lname, age, /, gender): pass # SyntaxError: / may appear only once def func(/, fname, lname, age, gender): pass # SyntaxError: at least one argument must precede / def func(fname, lname, /, age, gender): print(fname, lname, age, gender) func("John", "Smith", 36, "Male") func("John", "Smith", age=36, gender="Male") func("John", "Smith", **{"age":36, "gender":"Male"}) func("John", "Smith", gender="Male", age=36) func("John", "Smith", **{"gender":"Male", "age":36,}) # John Smith 36 Male func(fname="John", lname="Smith", age=36, gender="Male") func(**{"fname":"John", "lname":"Smith", "age":36, "gender":"Male"}) # TypeError: func() got some positional-only arguments passed # as keyword arguments: 'fname, lname' def func(fname, lname, age, gender, /): print(fname, lname, age, gender) func("John", "Smith", 36, "Male") # John Smith 36 Male func(fname="John", lname="Smith", age=36, gender="Male") func(**{"fname":"John", "lname":"Smith", "age":36, "gender":"Male"}) # TypeError: func() got some positional-only arguments passed # as keyword arguments: 'fname, lname, age, gender' <Optional parameters>:
def func(fname="John", lname="Smith", /, age=36, gender="Male"): pass def func(fname="John", lname="Smith", age=36, gender="Male", /): pass # No error def func(fname="John", /, lname="Smith", age=36, /, gender="Male"): pass # SyntaxError: / may appear only once def func(/, fname="John", lname="Smith", age=36, gender="Male"): pass # SyntaxError: at least one argument must precede / def func(fname="John", lname="Smith", /, age=36, gender="Male"): print(fname, lname, age, gender) func() # John Smith 36 Male func("Anna", "Brown", 27, "Female") func("Anna", "Brown", age=27, gender="Female") func("Anna", "Brown", **{"age":27, "gender":"Female"}) func("Anna", "Brown", gender="Female", age=27) func("Anna", "Brown", **{"gender":"Female", "age":27}) # Anna Brown 27 Female func(fname="Anna", lname="Brown", age=27, gender="Female") func(**{"fname":"Anna", "lname":"Brown", "age":27, "gender":"Female"}) # TypeError: func() got some positional-only arguments passed # as keyword arguments: 'fname, lname' def func(fname="John", lname="Smith", age=36, gender="Male", /): print(fname, lname, age, gender) func() # John Smith 36 Male func("Anna", "Brown", 27, "Female") # Anna Brown 27 Female func(fname="Anna", lname="Brown", age=27, gender="Female") func(**{"fname":"Anna", "lname":"Brown", "age":27, "gender":"Female"}) # TypeError: func() got some positional-only arguments passed # as keyword arguments: 'fname, lname, age, gender' 
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