2.3. Star Parameters¶
*is used for positional parametersargsis a convention, but you can use any name*argsunpacks totuple**is used for keyword parameterskwargsis a convention, but you can use any name**kwargsunpacks todict
2.3.1. Syntax¶
>>> def myfunction(*args):
... pass
>>> def myfunction(**kwargs):
... pass
>>> def myfunction(*args, **kwargs):
... pass
2.3.2. Recap¶
Parameter - Receiving variable used within the function
Required parameters - Parameter which is necessary to call function
Optional parameters - Parameter which is optional and has default value (if not specified at call time)
Optional parameter - also known as: parameter with default value
Required parameters:
>>> def echo(a, b):
... pass
Optional parameters:
>>> def echo(a=1, b=2):
... pass
Required and optional parameters:
>>> def echo(a, b=2):
... pass
Required parameters must be the leftmost:
>>> def echo(a=1, b):
... pass
Traceback (most recent call last):
SyntaxError: non-default argument follows default argument
2.3.3. Positional Parameters¶
*is used for positional parametersargsis a convention, but you can use any name*argsunpacks totuple
>>> def echo(*args):
... print(f'{args=}')
>>>
>>>
>>> echo()
args=()
>>>
>>> echo(1)
args=(1,)
>>>
>>> echo(2, 3)
args=(2, 3)
>>>
>>> echo(1, 2, 3, 4, 5)
args=(1, 2, 3, 4, 5)
2.3.4. Keyword Parameters¶
**is used for keyword parameterskwargsis a convention, but you can use any name**kwargsunpacks todict
>>> def echo(**kwargs):
... print(f'{kwargs=}')
>>>
>>>
>>> echo()
kwargs={}
>>>
>>> echo(a=1)
kwargs={'a': 1}
>>>
>>> echo(a=1, b=2)
kwargs={'a': 1, 'b': 2}
>>>
>>> echo(a=1, b=2, c=3, d=4, e=5)
kwargs={'a': 1, 'b': 2, 'c': 3, 'd': 4, 'e': 5}
2.3.5. Positional and Keyword Parameters¶
*is used for positional parameters**is used for keyword parameters*argsunpacks totuple**kwargsunpacks todict
>>> def echo(*args, **kwargs):
... print(f'{args=}, {kwargs=}')
>>>
>>>
>>> echo()
args=(), kwargs={}
>>>
>>> echo(1, 2, 3)
args=(1, 2, 3), kwargs={}
>>>
>>> echo(d=4, e=5, f=6)
args=(), kwargs={'d': 4, 'e': 5, 'f': 6}
>>>
>>> echo(1, 2, 3, d=4, e=5, f=6)
args=(1, 2, 3), kwargs={'d': 4, 'e': 5, 'f': 6}
2.3.6. Parameters with Args, Kwargs¶
>>> def echo(a, b, c=None, *args):
... print(f'{a=}, {b=}, {c=}, {args=}')
>>>
>>>
>>> echo(1, 2)
a=1, b=2, c=None, args=()
>>>
>>> echo(1, 2, 3)
a=1, b=2, c=3, args=()
>>>
>>> echo(1, 2, 3, 4)
a=1, b=2, c=3, args=(4,)
>>>
>>> echo(1, 2, 3, 4, 5, 6)
a=1, b=2, c=3, args=(4, 5, 6)
>>> def echo(a, b, c=None, **kwargs):
... print(f'{a=}, {b=}, {c=}, {kwargs=}')
>>>
>>>
>>> echo(1, 2)
a=1, b=2, c=None, kwargs={}
>>>
>>> echo(1, 2, 3)
a=1, b=2, c=3, kwargs={}
>>>
>>> echo(1, 2, 3, d=7, e=8, f=9)
a=1, b=2, c=3, kwargs={'d': 7, 'e': 8, 'f': 9}
>>>
>>> echo(1, 2, a=7)
Traceback (most recent call last):
TypeError: echo() got multiple values for argument 'a'
>>> def echo(a, b, c=None, *args, **kwargs):
... print(f'{a=}, {b=}, {c=}, {args=}, {kwargs=}')
>>>
>>>
>>> echo(1, 2)
a=1, b=2, c=None, args=(), kwargs={}
>>>
>>> echo(1, 2, 3, 4, 5, 6)
a=1, b=2, c=3, args=(4, 5, 6), kwargs={}
>>>
>>> echo(1, 2, 3, d=7, e=8, f=9)
a=1, b=2, c=3, args=(), kwargs={'d': 7, 'e': 8, 'f': 9}
>>>
>>> echo(1, 2, 3, 4, 5, 6, d=7, e=8, f=9)
a=1, b=2, c=3, args=(4, 5, 6), kwargs={'d': 7, 'e': 8, 'f': 9}
2.3.7. Merge¶
>>> def echo(a,b,c,d,e):
... return locals()
...
...
>>> data1 = {'a':1, 'b':2, 'c':3}
>>> data2 = {'d':4, 'e':5}
>>>
>>> echo(**data1, **data2)
{'a': 1, 'b': 2, 'c': 3, 'd': 4, 'e': 5}
Merging dicts before Python 3.9:
>>> {**data1, **data2}
{'a': 1, 'b': 2, 'c': 3, 'd': 4, 'e': 5}
Merging dicts since Python 3.9:
>>> data1 | data2
{'a': 1, 'b': 2, 'c': 3, 'd': 4, 'e': 5}
2.3.8. Use Case - 0x01¶
>>> def add(*values):
... total = 0
... for value in values:
... total += value
... return total
>>>
>>>
>>> add()
0
>>>
>>> add(1)
1
>>>
>>> add(1, 4)
5
>>>
>>> add(3, 1)
4
>>>
>>> add(1, 2, 3, 4)
10
2.3.9. Use Case - 0x02¶
>>> def celsius_to_kelvin(*degrees):
... return [x+273.15 for x in degrees]
>>>
>>>
>>> celsius_to_kelvin(1)
[274.15]
>>>
>>> celsius_to_kelvin(1, 2, 3, 4, 5)
[274.15, 275.15, 276.15, 277.15, 278.15]
2.3.10. Use Case - 0x03¶
>>> def html_list(*fruits):
... print('<ul>')
... for fruit in fruits:
... print(f'<li>{fruit}</li>')
... print('</ul>')
>>>
>>>
>>> html_list('apple', 'banana', 'orange')
<ul>
<li>apple</li>
<li>banana</li>
<li>orange</li>
</ul>
2.3.11. Use Case - 0x04¶
Intuitive definition of print function:
>>> print('hello')
hello
>>>
>>> print('hello', 'world')
hello world
>>>
>>> print('hello', 'new', 'world')
hello new world
>>> def print(*values, sep=' ', end='\n'):
... return sep.join(values) + end
2.3.12. Assignments¶
"""
* Assignment: Star Parameters Define
* Complexity: easy
* Lines of code: 4 lines
* Time: 5 min
English:
1. Create function `mean()`, which calculates arithmetic mean
2. Function can have arbitrary number of positional arguments
Polish:
1. Napisz funkcję `mean()`, wyliczającą średnią arytmetyczną
2. Funkcja przyjmuje dowolną ilość pozycyjnych argumentów
Non-functional requirements:
* Do not import any libraries and modules
* Use builtin functions `sum()` and `len()`
* Run doctests - all must succeed
Hints:
* `raise ValueError('error message')`
* `sum(...) / len(...)`
Tests:
>>> import sys; sys.tracebacklimit = 0
>>> mean(1)
1.0
>>> mean(1, 2)
1.5
>>> mean(1, 2, 3)
2.0
>>> mean(1, 2, 3, 4)
2.5
>>> mean()
Traceback (most recent call last):
ValueError: At least one argument is required
"""
"""
* Assignment: Star Parameters Args
* Complexity: easy
* Lines of code: 6 lines
* Time: 8 min
English:
1. Create function `isnumeric`
2. Function can have arbitrary number of positional arguments
3. Arguments can be of any type
4. Return `True` if all arguments are `int` or `float` only
5. Return `False` if any argument is different type
6. Do not use `all()` and `any()`
7. Run doctests - all must succeed
Polish:
1. Stwórz funkcję `isnumeric`
2. Funkcja może przyjmować dowolną liczbę argumentów pozycyjnych
3. Podawane argumenty mogą być dowolnego typu
4. Zwróć `True` jeżeli wszystkie argumenty są tylko typów `int` lub `float`
5. Zwróć `False` jeżeli którykolwiek jest innego typu
6. Nie używaj `all()` oraz `any()`
7. Uruchom doctesty - wszystkie muszą się powieść
Hints:
* `isinstance(obj, type1|type2)`
* `type(obj)`
* `len()`
Tests:
>>> import sys; sys.tracebacklimit = 0
>>> from inspect import isfunction
>>> assert isfunction(isnumeric), \
'isnumeric must be a function'
>>> isnumeric()
False
>>> isnumeric(0)
True
>>> isnumeric(1)
True
>>> isnumeric(-1)
True
>>> isnumeric(1.1)
True
>>> isnumeric('one')
False
>>> isnumeric([1, 1.1])
False
>>> isnumeric(1, 1.1)
True
>>> isnumeric(1, 'one')
False
>>> isnumeric(1, 'one', 'two')
False
>>> isnumeric(True)
False
"""
# Return True if all arguments are int or float, otherwise False
# type: Callable[[int|float],bool]
def isnumeric(*args):
...
"""
* Assignment: Star Parameters Kwargs
* Complexity: medium
* Lines of code: 7 lines
* Time: 8 min
English:
1. Create function `isnumeric`
2. Function takes arbitrary number of positional and keyword arguments
3. Arguments can be of any type
4. Return `True` if all arguments are `int` or `float` only
5. Return `False` if any argument is different type
6. Do not use `all()` and `any()`
7. Compare using `type()` and `isinstance()` passing `True` as an argument
8. Run the function without any arguments
9. Run doctests - all must succeed
Polish:
1. Stwórz funkcję `isnumeric`
2. Funkcja przyjmuje dowolną liczbę argumentów pozycyjnych i nazwanych
3. Podawane argumenty mogą być dowolnego typu
4. Zwróć `True` jeżeli wszystkie argumenty są tylko typów `int` lub `float`
5. Zwróć `False` jeżeli którykolwiek jest innego typu
6. Nie używaj `all()` oraz `any()`
7. Porównaj użycie `type()` i `isinstance()` podając `True` jako argument
8. Uruchom funkcję bez podawania argumentów
9. Uruchom doctesty - wszystkie muszą się powieść
Hints:
* `isinstance(obj, (type1, type2))`
* `type(obj)`
* `len()`
* `dict.values()`
* `tuple() + tuple()`
Tests:
>>> import sys; sys.tracebacklimit = 0
>>> from inspect import isfunction
>>> assert isfunction(isnumeric), \
'isnumeric must be a function'
>>> isnumeric()
False
>>> isnumeric(0)
True
>>> isnumeric(1)
True
>>> isnumeric(-1)
True
>>> isnumeric(1.1)
True
>>> isnumeric('one')
False
>>> isnumeric([1, 1.1])
False
>>> isnumeric(1, 1.1)
True
>>> isnumeric(1, 'one')
False
>>> isnumeric(1, 'one', 'two')
False
>>> isnumeric(True)
False
>>> isnumeric(a=1)
True
>>> isnumeric(a=1.1)
True
>>> isnumeric(a='one')
False
"""
# Return True if all arguments are int or float, otherwise False
# type: Callable[[int|float],bool]
def isnumeric(*args, **kwargs):
...