User define Functions:
- In Python, a user-defined functions declaration begins with the keyword def followed by the function name.
- To access the functions we need to call them, without calling the function we cannot access the functions.
Syntax:
def function_name(parameters) :
Statements
- - -
- - -
return values
Note: Here, return is an optional statement.
Example: Write a function to print the addition of two variables.
1) def addition() :
2) a,b = 10,20
3) print("Addition of two variables: ", (a+b))
4) addition() #Function calling
output:
Addition of two variables: 30
Parameters:
A parameter is a special kind of variable they are used to input the value to the function. If a function contains parameters, then at the time of the function call, we should provide values otherwise, it will get an error.
Example: Write a function to print the addition of two variables using parameter input.
1) def addition(a, b) :
2) print("Addition of two variables: ", (a+b))
3) addition(10, 20)
4) addition(2.5, 5.2)
output:
Addition of two variables: 30
Addition of two variables: 7.6
Return Statements:
A return statement is used to return a value from a function.
Example 1:
1) def add(a, b) :
2) c = a+b
3) return c
4) x = add(10, 20)
5) print(x) #30
Example 2:
1) def num() :
2) a = 10
3) b = 20
3) return a,b
4) x, y = num()
5) print(x+y) #30
Function Arguments:
Syntax:
def add(a, b) :
- - -
- - -
add(10, 20)
Here a, b are formal arguments whereas 10, 20 are actual arguments.
There are 4 types of actual arguments in Python.
1) positional arguments
2) keyword arguments
3) default arguments
4) arbitrary arguments (Variable length arguments)
1) positional arguments:
These are the arguments passed to function in the correct positional order.
Eg:
def add(a, b) :
print(a+b)
add(10, 20) #30
add(10, 20, 30) #TypeError:
The function must be called with the correct number of arguments, not more and not less.
2) keyword arguments:
We can pass argument values by parameter names.
Eg:
1) def sub(a, b) :
2) print(a-b)
3) sub(a=20, b=10) #10
4) sub(b=20, a=10) #-10
5) sub(b=10, a=20) #10
6) sub(20, b=10) #10
7) sub(a=20, 10) #SyntaxError:
3) default arguments:
We can provide default values to function arguments.
Eg:
1) def add(a=10, b=20)
2) print("Sum: ", a+b)
3) add() #Sum: 30
4) add(2, 3) #Sum: 5
5) add(5, b=15) #Sum: 20
6) add(a=5, 8) #SyntaxError:
4) arbitrary arguments/variable length arguments:
- If you do not know how many arguments that will be passed into your function then in that case we will use these arbitrary arguments.
- We can declare an arbitrary argument by adding the * symbol before the parameter name in the function definition.
- We can call the function by passing any number of arguments including zero number. Internally all these values are represented in the form of tuple.
Eg:
1) def add(*n) :
2) total = 0
3) for i in n :
4) total = total + i
5) print("Addition : ", total)
6) add() #Addition : 0
7) add(10) #Addition : 10
8) add(10, 20) #Addition : 30
Eg:
1) def tc(a, *n) :
2) print(a)
3) for i in n :
4) print(i)
5) tc(10) #10
6) tc(10, "A", "B", "C") #10, A, B, C
Eg: After an arbitrary argument, if we are taking any other arguments we should provide values as keyword arguments.
1) def tc(*n, a) :
2) print(a)
3) for i in n:
4) print(i)
5) tc("A", "B", "C", a=10) #A B C 10
6) tc("A", "B", "C", 10) # Error
* * * * * * * * * * * * * * * * * * * * *
- We can also declare an arbitrary argument by adding the ** symbol before the parameter name in the function definition.
- We can call the function by passing any number of keyword arguments. Internally all these values are represented in the form of a dictionary.
Eg:
1) def testing(**tc) :
2) for x,y in tc.items() :
3) print(x, "=", y)
4) testing(a=10,b=20, c="colleges")
#output:
a = 10
b = 20
c = colleges
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