Functions in Python

5 Key excerpts on "Functions in Python"

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  eBook - ePub

  Learn Web Development with Python

  Get hands-on with Python Programming and Django web development

  • Fabrizio Romano, Gaston C. Hillar, Arun Ravindran(Authors)
  • 2018(Publication Date)
  • Packt Publishing

    (Publisher)

  Functions, the Building Blocks of Code

  "To create architecture is to put in order. Put what in order? Functions and objects."  – Le Corbusier

  In the previous chapters, we have seen that everything is an object in Python, and functions are no exception. But, what exactly is a function? A function is a sequence of instructions that perform a task, bundled as a unit. This unit can then be imported and used wherever it's needed. There are many advantages to using functions in your code, as we'll see shortly.

  In this chapter, we are going to cover the following:

  • Functions—what they are and why we should use them
  • Scopes and name resolution
  • Function signatures—input parameters and return values
  • Recursive and anonymous functions
  • Importing objects for code reuse

  I believe the saying, a picture is worth one thousand words , is particularly true when explaining functions to someone who is new to this concept, so please take a look at the following diagram:

  As you can see, a function is a block of instructions, packaged as a whole, like a box. Functions can accept input arguments and produce output values. Both of these are optional, as we'll see in the examples in this chapter.

  A function in Python is defined by using the def keyword, after which the name of the function follows, terminated by a pair of parentheses (which may or may not contain input parameters), and a colon (:) signals the end of the function definition line. Immediately afterwards, indented by four spaces, we find the body of the function, which is the set of instructions that the function will execute when called.

  Note that the indentation by four spaces is not mandatory, but it is the amount of spaces suggested by PEP 8 , and, in practice, it is the most widely used spacing measure.

  A function may or may not return an output. If a function wants to return an output, it does so by using the return keyword, followed by the desired output. If you have an eagle eye, you may have noticed the little * after Optional

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  eBook - ePub

  Programming in Python

  Learn the Powerful Object-Oriented Programming

  • Dr. Pooja Sharma(Author)
  • 2018(Publication Date)
  • BPB Publications

    (Publisher)

  HAPTER 6

  Python Functions

  Highlights

  • Python functions
  • Types of functions
  • Advantages of functions
  • Python user defined functions
  • Python anonymous functions
  • Pass by value vs. pass by reference
  • Recursion

  In programming, sometimes a similar code has to be repeated at many places in a program. For which, the programmer needs to write the same set of instructions several times. For example, while computing a binomial coefficient, the factorial needs to be computed several times. It would waste the programmer's time and effort to write the same code again and again. This activity not only increases the size of the program but also leads to typographical errors. To overcome this issue, the Python programming language is provided with the feature called subprograms or functions. A subprogram or function is a name given to a set of instructions that can be called by another program or a subprogram. This technique simplifies the programming process to a great extent because a single set of instructions in the form of a subprogram is being used for all instances of computational requirements with only change in the supplied data.

  6.1. Python Functions

  In Python programming language, a function is a self-contained group of statements, which are intended to perform a specific task. Functions break the program into smaller modules, which perform a particular operation and are easy to understand. The large programs become more manageable and organized by using the concept of functions.

  6.2. Advantages of Functions

  1. Avoids Repetition: functions avoid repetition of the similar code again and again. The same code of a function can be used several times by different parts of the program or by different programs.
  2. Modularization:

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  eBook - ePub

  Python Made Simple

  Learn Python programming in easy steps with examples

  • Rydhm Beri(Author)
  • 2019(Publication Date)
  • BPB Publications

    (Publisher)

  HAPTER 5

  Functions

  Introduction

  A function is a self-contained block of statements that can repeatedly be executed whenever we need it in a program. The concept of a function is very useful and is used in every programming language like C, C++, Java, Python, and so on. Functions are used to provide the functional programming feature to the programming language. Some languages like C, C++, and Java do not allow you to write even a single program without using functions. But in Python, we can create our programs even without using functions. The advantage of functions while writing a Python program is that it allows the programmer to include extra features in the Python program. In this chapter, we will focus on Python functions. We will describe the different types of functions used in a Python program. We will also discuss the different methods used to pass arguments to the functions and other concepts related to the functions.

  Structure

  • Introduction to functions
  • Difference between functions and methods
  • Advantages of using functions
  • Classification of functions
  • Components of user-defined functions
  • Categories of functions
  • Passing Argument to functions
  • Scope of a variable
  • Recursion
  • Lambda functions

  Objectives

  • Understanding the concept of functions and their usage in programming
  • Understanding the classification of functions
  • Understanding the different components of functions
  • Knowing the parameter passing techniques of a function
  • Understanding the concept of recursion
  • Knowing the role of lambda functions

  Introduction to functions

  Python programming is useful to solve large problems in an easy and efficient manner. Sometimes, it is difficult to solve the complex problems at large extent. In order to manage complex problems, they can be broken down into the smaller subproblems, then these subproblems can be solved separately; this reduces the complexity of the program. These subproblems are considered as program routines.

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  eBook - ePub

  Python for Everyone

  Learn and polish your coding skills in Python (English Edition)

  • Saurabh Chandrakar, Dr. Nilesh Bhaskarrao Bahadure(Authors)
  • 2023(Publication Date)
  • BPB Publications

    (Publisher)

  HAPTER 6

  Concept of Functions in Python

  Introduction

  Sometimes during programming a code, we are required to use the same code again and again. As per the Don’t Repeat Yourself (DRY ) concept, the same code should not be repeated multiple times during programming. Nonetheless, sometimes we need to use a block of code multiple times. In such cases, Functions in Python come handy.

  Functions play a huge role in our Python code. An important point to note is that functions must be defined initially before being later called in Python with proper indentation. Functions in Python are important as a coder, because DRY concept must be respected, while creating any big project makes that any 3rd party coder understand its importance.

  Structure

  In this chapter, we will discuss the following topics:

  • Functions in Python
  • Function types
  • Function arguments
  • Nested function
  • Python closures
  • Function passing as a parameter
  • Local, global, and non-local variables
  • Recursive function
  • Python lambda functions

  Objectives

  By the end of this chapter, the reader will have an idea about what exactly function is in Python. They will have a taste of various arguments such as positional, keyword, default, *args and **kwargs. The concept of local, global, and non-local variables will be well explained. We shall see how to bind the data to a function without passing them as parameters called closures. One function will be defined inside another function using nested function concept. We shall see recursive function, that is, a function calling itself. Anonymous functions taking any number of arguments with one expression will be seen by exploring the concept of lambda functions.

  Functions in Python

  It is not recommended to write group of statements repeatedly to execute the program. The group of statements will be defined as a single unit, thus breaking our program into smaller and modular chunks. We name this group of statements as functions, which performs a specific task. Code reusability is possible and repetition is avoided. We will be writing function only once, but the function will be called multiple times. The basic syntax of function is as follows:

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  eBook - ePub

  Introduction to Python Programming

  • Gowrishankar S, Veena A(Authors)
  • 2018(Publication Date)
  • Chapman and Hall/CRC

    (Publisher)

  4 Functions

  AIM Learn to define and invoke functions and comprehend the use of arguments and parameters to pass information to a function as well as return information from a function. LEARNING OUTCOMES At the end of this chapter, you are expected to •  Understand the purpose of Functions in Python. •  Define and invoke functions. •  Receive the returned data from functions. •  Understand the use of modules and built-in Functions in Python. •  Determine the scope of variables. •  Recognize different forms of function arguments.

  Functions are one of the fundamental building blocks in Python programming language. Functions are used when you have a block of statements that needs to be executed multiple times within the program. Rather than writing the block of statements repeatedly to perform the action, you can use a function to perform that action. This block of statements are grouped together and is given a name which can be used to invoke it from other parts of the program. You write a function once but can execute it any number of times you like. Functions also reduce the size of the program by eliminating rudimentary code. Functions can be either Built-in Functions or User-defined functions.

  4.1    Built-In Functions

  The Python interpreter has a number of functions that are built into it and are always available. You have already looked at some of the built-in functions like input(), print(), range() and others in previous chapters. Let’s discuss few more built-in functions (TABLE 4.1

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