*Memos:
- My post explains a function.
- My post explains parameters and arguments in function.
- My post explains keyword-only parameters in function.
- My post explains positional-only parameters and keyword-only parameters together in function.
You can set positional-only parameters for a function as shown below:
*Memos:
- 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.
The parameters without default values:
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'
The parameters with default values:
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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