Arguments
Information can be passed into functions as arguments.
Arguments are specified after the function name, inside the parentheses. You can add as many arguments as you want, just separate them with a comma.
The following example has a function with one argument [fname]. When the function is called, we pass along a first name, which is used inside the function to print the full name:
Example
def
my_function[fname]:
print[fname + " Refsnes"]
my_function["Emil"]
my_function["Tobias"]
my_function["Linus"]
Try it Yourself »
Arguments are often shortened to args in Python documentations.
Parameters or Arguments?
The terms parameter and argument can be used for the same thing: information that are passed into a function.
From a function's perspective:
A parameter is the variable listed inside the parentheses in the function definition.
An argument is the value that are sent to the function when it is called.
Number of Arguments
By default, a function must be called with the correct number of arguments. Meaning that if your function expects 2 arguments, you have to call the function with 2 arguments, not more, and not less.
Example
This function expects 2 arguments, and gets 2 arguments:
def my_function[fname, lname]:
print[fname + " " + lname]
my_function["Emil", "Refsnes"]
Try it Yourself »
If you try to call the function with 1 or 3 arguments, you will get an error:
Example
This function expects 2 arguments, but gets only 1:
def my_function[fname, lname]:
print[fname + " " + lname]
my_function["Emil"]
Try it Yourself »
A function can take multiple arguments, these arguments can be objects, variables[of same or different data types] and functions. Python functions are first class objects. In the example below, a function is assigned to a variable. This assignment doesn’t call the function. It takes the function object referenced by shout and creates a second name pointing to it, yell.
def shout[text]:
return text.upper[]
print[shout['Hello']]
yell = shout
print[yell['Hello']]
Output:
HELLO HELLO
Higher Order Functions
Because functions are objects we can pass them as arguments to other functions. Functions that can accept other functions as arguments are also called higher-order functions. In the example below, a function greet is created which takes a function as an argument.
def shout[text]:
return text.upper[]
def whisper[text]:
return text.lower[]
def greet[func]:
greeting = func["Hi, I am created by a function passed as an argument."]
print[greeting]
greet[shout]
greet[whisper]
Output
HI, I AM CREATED BY A FUNCTION PASSED AS AN ARGUMENT. hi, i am created by a function passed as an argument.
Wrapper function
Wrapper function or decorator allows us to wrap another function in order to extend the behavior of the wrapped function, without permanently modifying it. In Decorators, functions are taken as the argument into another function and then called inside the wrapper function. To know more about decorator click here.
Below is the example of a simple decorator.
def hello_decorator[func]:
def inner1[]:
print["Hello, this is before function execution"]
func[]
print["This is after function execution"]
return inner1
def function_to_be_used[]:
print["This is inside the function !!"]
function_to_be_used = hello_decorator[function_to_be_used]
function_to_be_used[]
Output:
Hello, this is before function execution This is inside the function !! This is after function execution
Lambda wrapper function
In Python, anonymous function means that a function is without a name. As we already know that def keyword is used to define the normal functions and the lambda keyword is used to create
anonymous functions. This function can have any number of arguments but only one expression, which is evaluated and returned. Lambda function can also have another function as an argument. The below example shows a basic lambda function where
another lambda function is passed as an argument.
square = lambda x:x * x
cube = lambda func:func**3
print["square of 2 is :"+str[square[2]]]
print["\nThe cube of "+str[square[2]]+" is " +str[cube[square[2]]]]
Output:
square of 2 is :4 The cube of 4 is 64