Functions are reusable program fragments. They allow you to name a block of code, allow you to run it anywhere in your program with that particular name, and repeat it any number of times. This is called Calling. Function.
Functions can be defined by the keyword def. This key is followed by the identifier name of a function, followed by a pair of parentheses, which can include the names of some variables, and then end the line with a colon. The subsequent block of statements is part of the function.
def say_hello():
# This block belongs to this function.
print('hello world')
# End of function
say_hello() # Calling function
say_hello() # Call the function again$ python function1.py
hello world
hello world 1. Functional parameters
The parameters in a function are specified by placing them in a pair of parentheses used to define the function and separated by commas. When we call a function, we provide the required values in the same form. The given name when defining a function is called "Parameters"
When calling a function, the value you provide to the function is called an Arguments.
def print_max(a, b):
if a > b:
print(a, 'is maximum')
elif a == b:
print(a, 'is equal to', b)
else:
print(b, 'is maximum')
# Pass literal values directly
print_max(3, 4)
x = 5
y = 7
# Transfer variables in the form of parameters
print_max(x, y)$ python function_param.py
4 is maximum
7 is maximum
2. Local variables
When variables are declared in the definition of a function, they do not in any way relate to variables that are outside the function but have the same name, that is to say, they only exist in the Local part of the function. This is called the Scope of variables.
x = 5
def func(x):
print('x is', x)
x = 2
print('Changed local x to', x)
func(x)
print('x is still', x)$ python function_local.py
x is 5
Changed local x to 2
x is still 5
Use global to assign a variable at the top of the program (that is, it does not exist in any scope, whether function or class) to tell Python This variable is not local, but Global.
x = 5
def func():
global x
print('x is', x)
x = 2
print('Changed global x to', x)
func()
print('Value of x is', x)$ python function_global.py
x is 5
Changed global x to 2
Value of x is 2
def func(a, b=5, c=10):
print('a is', a, 'and b is', b, 'and c is', c)
func(3, 7)
func(25, c=24)
func(c=50, a=100)$ python function_keyword.py
a is 3 and b is 7 and c is 10
a is 25 and b is 5 and c is 24
a is 100 and b is 5 and c is 50
def total(a=5, *numbers, **phonebook):
print('a', a)
#Traversing through all items in tuples
for single_item in numbers:
print('single_item', single_item)
#Traversing through all items in a dictionary
for first_part, second_part in phonebook.items():
print(first_part,second_part)
print(total(10,1,2,3,Jack=1123,John=2231,Inge=1560))$ python function_varargs.py
a 10
single_item 1
single_item 2
single_item 3
Jack 1123
Inge 1560
John 2231
None
7. DocStrings
def print_max(x, y):
'''Prints the maximum of two numbers.Print the maximum of two values.
The two values must be integers.Both numbers should be integers.'''
# Convert it to integer type if possible
x = int(x)
y = int(y)
if x > y:
print(x, 'is maximum')
else:
print(y, 'is maximum')
print_max(3, 5)
print(print_max.__doc__)$ python function_docstring.py
5 is maximum
Prints the maximum of two numbers.
The two values must be integers