Introduction
Python is a powerful language that allows you to quickly and effectively express your ideas. The ability to use functions with this language is one of its greatest strengths, as it can drastically reduce development time and allow you to create more sophisticated programs. In this article, we'll be explaining exactly how functions work in Python so that anyone, regardless of experience level, can make the most out of their programming endeavors. So if you're looking for a better way to get things done with Python, keep reading!
What are functions in the Python?
Python functions provide a way to organize related snippets of code. Creating functions is also beneficial because functions allow users to call on them at any point in the program without needing to know exactly how their functions work as it simplifies and streamlines programs and makes them easier to manage. Functions can also be used with data for larger-scale tasks and can include parameters, conditional statements, loops, and so much more. As such, functions are an incredibly useful tool when coding in Python.
How to define a function in python
Defining a function in python is relatively straightforward, as python comes with many pythons built in functions that can be called upon to achieve desired outcomes. Creating custom python functions starts by using the 'def' keyword followed by the name of the function. After this point, variables and other python instructions can then be used to craft precisely what the user wants the function to do. It is important to provide meaningful names for the python functions so that other developers who may use the code can easily identify what the function does without having to look into its inner workings. Once defined, python functions can be called within other commands, drastically simplifying more complex logic and keeping all related code together.
Syntax
def functionname( parameters ):
"function_docstring"
function_suite
return [expression]
Example
def printme( str ):
"This prints a passed string into this function"
print str
return
How to call a function in python
Calling a python function is relatively straightforward and simple, provided its user knows what parameters it expects to receive. All python functions have a specific purpose, so make sure to research the function before calling it. When calling a python function, remember to place parentheses after the name of the function which contains any relevant parameters. If no arguments need to be passed in, the parentheses will simply remain empty. Beyond this, python functions do not require any additional information; simply type out the function name and watch as python does its work.
Example
# Function definition is here
def printme( str ):
"This prints a passed string into this function"
print str
return;
# Now you can call printme function
printme("I am the first call to a user-defined function!")
printme("Again a second call to the same function")
Output
I am the first call to a user-defined function!
Again a second call to the same function
Pass by value and Pass by reference in Python
Pass by value in python
In Python, pass by value is a method of passing arguments to functions. This means that when an argument is passed to a function, the Python interpreter evaluates the expression and passes its value rather than the expression itself to the function. This allows the program to do more with fewer lines of code, as well as resulting in faster execution. Pass by value also helps Python be secure against external influences or user mistakes that could lead to unexpected or unwanted results. By passing only values, it prevents external influences from affecting the program's run-time environment. Pass by value becomes especially important when dealing with large-scale applications in Python that require highly optimized code for efficient execution.
Example
student = {'Ram': 12, 'Rahul': 14, 'Rajan': 10}
def test(student):
student = {'Shyam':20, 'Shivam':21}
print("Inside the function", student)
return
test(student)
print("Outside the function:", student)
Pass by reference in python
When programming in Python, pass by reference can help to save a lot of time when trying to pass values between functions and classes. Pass by reference allows for direct object modification, meaning the user doesn't have to work with copies of variables or pass every piece of data back and forth between functions. Essentially, pass by reference creates a link from one object to another, which can then be used in the program. As such, pass by reference should be considered any time the developer is performing multiple operations on an existing object without needing to create further copies.
Example
student = {'Ram': 12, 'Rahul': 14, 'Rajan': 10}
def test(student):
new = {'Shyam':20, 'Shivam':21}
student.update(new)
print("Inside the function", student)
return
test(student)
print("Outside the function:", student)
Function Arguments
In this particular language, there are 4 types of function arguments, Those are
- Required arguments
- Keyword arguments
- Default arguments
- Variable-length arguments
Required arguments in python
Required arguments in Python are parameters that must be provided for a function to be able to successfully run. Any arguments that are not required may be omitted, but the required ones must appear in the appropriate syntax with the correct amount of data included. Required arguments are necessary for functions to properly run their process and get the desired output result. Required argument values are placed in their designated positions when calling upon a function, ensuring that all necessary details have been provided. Python's requirement of strict adherence allows users to access the full potential of functions as intended by its developers.
Example
# Function definition is here
def printme( str ):
"This prints a passed string into this function"
print str
return;
# Now you can call printme function
printme()
Output
Traceback (most recent call last):
File "test.py", line 11, in <module>
printme();
TypeError: printme() takes exactly 1 argument (0 given)
Keyword arguments in python
Keyword arguments in Python are a crucial part of coding and understanding the applications within Python. Keyword arguments specify the names and associated values for parameters passed into a function, allowing them to be used in an organized and standardized way. Keyword arguments help reduce confusion between positional and keyword argument syntax, ensuring correct argument usage without requiring memorization. Keyword arguments make it possible for the user to use functions more efficiently, freeing up their thinking energy for tackling bigger challenges. Keywords represent an important language feature that can help make that particular code concise, clean, and most importantly very effective.
Example
# Function definition is here
def printme( str ):
"This prints a passed string into this function"
print str
return;
# Now you can call printme function
printme( str = "My string")
Output
My string
Default arguments in python
Default arguments in Python allow developers to define default values within certain functions. This has the benefit of minimizing code duplication since the same default argument can be used across multiple functions. Additionally, it allows for greater flexibility when using a function in terms of what parameters need to be passed in. Default arguments enable a programmer to call a function without assigning specific values for arguments, as long as each argument has an associated default value. This is a useful feature that simplifies and enhances the programming environment, allowing developers to code more efficiently and effectively.
Example
# Function definition is here
def printinfo( name, age = 35 ):
"This prints a passed info into this function"
print "Name: ", name
print "Age ", age
return;
# Now you can call printinfo function
printinfo( age=20, name="Urmi" )
printinfo( name="Urmi" )
Output
Name: Urmi
Age 20
Name: Urmi
Age 35
Variable-length arguments in python
Variable-length arguments in python can be a powerful tool for developers. These arguments allow changes to be made to a function while still being able to use the same function signature. Variable-length arguments can be used as both positional and keyword arguments, allowing for greater flexibility when writing code. Variable-length arguments also have the ability to accept an arbitrary number of unknown elements, making them ideal for dealing with infinite sets of data. By taking advantage of variable-length arguments in python, developers can write clear and concise code that is more efficient than in other programming languages.
Example
# Function definition is here
def printinfo( arg1, *vartuple ):
"This prints a variable passed arguments"
print "Output is: "
print arg1
for var in vartuple:
print var
return;
# Now you can call printinfo function
printinfo( 10 )
printinfo( 70, 60, 50 )
Output
Output is:
10
Output is:
70
60
50
Anonymous Functions in python
Anonymous functions in python are incredibly useful for quickly writing simple, single-use functions which don't require a full definition. Anonymous functions take the form of lambda expressions, where the user passes particular parameters through a single expression. These functions can then be used in places where the developer would use any other type of function, such as with the map or filter constructors. Anonymous functions are essential tools when dealing with higher-order functions such as reduce, which is used to condense a sequence of data into one value. Anonymous Functions allow for concise code that would otherwise require several lines to write, making them important to bear in mind when programming with python.
Syntax
lambda [arg1 [,arg2,.....argn]]:expression
Example
# Function definition is here
sum = lambda arg1, arg2: arg1 + arg2;
# Now you can call sum as a function
print "Value of total : ", sum( 10, 20 )
print "Value of total : ", sum( 20, 20 )
Output
Value of total : 30
Value of total : 40
The return Statement in Python
The return statement in python is an essential component of writing functions and creating efficient code. A return statement is used to return a value from a function and can be placed anywhere within the body of the code. Examples of using return statements include when we need to return multiple values or objects as part of a larger expression or program. Additionally, the use of return statement in python facilitate dynamic programming, and manipulating data, and also help when dealing with large datasets. Writing return statements can be tricky at times because they require accuracy due to the python language’s specific syntax rules; however, mastering return statements can be incredibly rewarding as they are some of the most powerful tools available in coding.
Example
# Function definition is here
def sum( arg1, arg2 ):
# Add both the parameters and return them."
total = arg1 + arg2
print "Inside the function : ", total
return total;
# Now you can call sum function
total = sum( 10, 20 );
print "Outside the function : ", total
Output
Inside the function : 30
Outside the function : 30Summary
We have seen that Python functions are incredibly useful and powerful. We can use them to efficiently perform operations, save time and resources, and give us greater control over our code. Python functions allow us to define specific tasks, pass parameters, receive return values, and even group related code into fewer lines of code. Using these techniques in our everyday coding will help make our work easier to maintain, reducing both development time and errors.
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