The World of Python Programming

Python Built-In Functions: A Complete Beginner’s Guide

Functions & Classes
目次

1. Introduction

Python is a programming language loved by a wide range of programmers, from beginners to professionals. One reason for its popularity is the set of built-in functions that Python provides. These built-in functions make it easy to perform the basic operations essential for writing programs, making them one of the key features beginners should learn first. The biggest appeal of built-in functions is their convenience. They are available as soon as Python is installed, without needing to install additional modules, so even first-time users can use them immediately. Also, commonly used functions have concise, intuitive names, making them easy to understand. For example, if you want to check the number of elements in a list you can use the len() function, and if you want to get the absolute value of a number you can use the abs() function, allowing you to complete the operation in a single line. This reduces the amount of code you need to write and improves code readability.

Why learn built-in functions?

Learning Python’s built-in functions is the first step toward significantly improving your programming efficiency. For the following reasons, people from beginners to advanced users should acquire knowledge of built-in functions.
  1. Code simplification By using built-in functions, you can express complex operations simply. For example, writing your own code to find the maximum value in a list would require multiple lines, but using the max() function completes it in a single line.
  2. Time savings Built-in functions are optimized by Python developers, so they run efficiently and quickly. Therefore, you can save time compared to implementing the process yourself.
  3. Avoiding errors Built-in functions are well tested and reliable, so they carry a lower risk of errors compared to functions you write yourself.

Overview of this article

In this article, we’ll explain Python’s built-in functions in the following order.
  • 2. What are Python’s built-in functions? This section explains the basic concepts and characteristics of built-in functions.
  • 3. Categories of built-in functions We’ll introduce commonly used functions by major categories such as numeric operations, sequence operations, and type conversions.
  • 4. Tips for learning Python’s built-in functions We’ll explain how to remember frequently used functions and efficient study methods.
  • 5. Summary We’ll recap the article and give advice on next steps.
To make it easy for beginners to understand, we’ll provide detailed explanations with code examples. By reading this article, you’ll learn the basic usage of Python’s built-in functions and gain skills to write programs more efficiently.

2. What are Python’s built-in functions?

Python’s built-in functions are handy tools at the core of Python programming. These functions are standard features provided by Python out of the box and can be used immediately without special configuration or importing modules. This section explains the basic characteristics and benefits of built-in functions in detail.

Overview of built-in functions

Built-in functions are functions embedded in the Python interpreter. They are available by default without adding libraries or packages to run your programs. Below are the main characteristics of built-in functions.
  1. Available immediately Built-in functions are included with your Python installation, so you can call them directly in your programs. For example, using the print() function as shown below lets you output a string to the screen.
   print("Hello, Python!")
  1. Highly versatile Built-in functions support a wide range of tasks such as numerical calculations, string manipulation, data type conversion, and list operations. This provides useful functionality for writing many kinds of programs.
  2. Pythonic design Following Python’s design philosophy, built-in functions are designed to be concise and intuitive. As a result, even first-time users can quickly understand and use them.

Advantages of built-in functions

Below are the main benefits of using Python’s built-in functions.

Code efficiency

Using built-in functions can significantly reduce the amount of code in your programs. For example, if you write code yourself to find the maximum value in a list, you would need to write code like the following.
numbers = [5, 3, 8, 2, 9]
max_value = numbers[0]
for num in numbers:
    if num > max_value:
        max_value = num
print(max_value)  # Output: 9
Using the max() function, you can write this in one line.
numbers = [5, 3, 8, 2, 9]
print(max(numbers))  # Output: 9

Reduce errors

Built-in functions are thoroughly tested by the Python development team, so their behavior is reliable. A major advantage is that they help you avoid bugs that commonly occur when implementing algorithms yourself.

Improved performance

Built-in functions are optimized in Python’s internal implementation. For that reason, they often run faster than equivalent code you write yourself.

Examples of built-in functions

Below are some commonly used Python built-in functions.
  1. len() Get the number of elements in a sequence (list, string, etc.).
   my_list = [10, 20, 30]
   print(len(my_list))  # Output: 3
  1. type() Check the data type of an object.
   print(type("Python"))  # Output: <class 'str'>
  1. sum() Sum the numbers in a list or tuple.
   numbers = [1, 2, 3, 4]
   print(sum(numbers))  # Output: 10
  1. sorted() Sort a sequence in ascending or descending order.
   scores = [70, 90, 80]
   print(sorted(scores))          # Output: [70, 80, 90]
   print(sorted(scores, reverse=True))  # Output: [90, 80, 70]
  1. input() Get input from the user.
   name = input("Please enter your name: ")
   print(f"Hello, {name}!")

Summary

Python’s built-in functions are fundamental tools for creating programs efficiently. Because of their convenience and versatility, they are among the important skills you should learn early when studying Python. In the next section, we’ll classify built-in functions by functionality and explain them with concrete examples to deepen your understanding.

3. Classification of Built-in Functions

Python includes many built-in functions with various capabilities. Classifying them by function makes it easier to learn and apply them effectively. In this section, we group Python’s built-in functions into common categories and explain their uses and examples in detail.

Numeric functions

These functions are used to manipulate numbers. They are useful for mathematical calculations and working with numerical properties.

Common functions

  1. abs(): Returns the absolute value of a number.
   print(abs(-10))  # Output: 10
  1. round(): Rounds a number to the specified number of digits.
   print(round(3.14159, 2))  # Output: 3.14
   print(round(2.718, 0))   # Output: 3.0
  1. pow(): Calculates the specified power of a number.
   print(pow(2, 3))  # Output: 8
  1. min() / max(): Returns the minimum or maximum value.
   numbers = [5, 3, 8, 2]
   print(min(numbers))  # Output: 2
   print(max(numbers))  # Output: 8

Sequence functions

Functions for operating on sequence data such as lists, tuples, and strings. They are frequently used for data processing and searching.

Common functions

  1. len(): Returns the number of elements in a sequence.
   my_list = [1, 2, 3, 4]
   print(len(my_list))  # Output: 4
  1. sorted(): Sorts a sequence in ascending or descending order.
   scores = [70, 90, 80]
   print(sorted(scores))          # Output: [70, 80, 90]
   print(sorted(scores, reverse=True))  # Output: [90, 80, 70]
  1. zip(): Combines multiple sequences element-wise.
   names = ["Alice", "Bob"]
   scores = [85, 90]
   print(list(zip(names, scores)))  # Output: [('Alice', 85), ('Bob', 90)]
  1. reversed(): Reverses a sequence.
   word = "Python"
   print("".join(reversed(word)))  # Output: nohtyP

Type conversion functions

Functions used to convert data types. They are especially useful when handling user input and data processing.

Common functions

  1. int(): Converts strings or floating-point numbers to integers.
   print(int("123"))  # Output: 123
   print(int(3.9))    # Output: 3
  1. float(): Converts strings or integers to floating-point numbers.
   print(float("3.14"))  # Output: 3.14
  1. str(): Converts numbers or objects to strings.
   print(str(123))  # Output: '123'
  1. list() / tuple(): Converts iterable objects to a list or tuple.
   my_tuple = (1, 2, 3)
   print(list(my_tuple))  # Output: [1, 2, 3]

Other useful functions

Functions with general-purpose features that don’t fit into a specific category. Many of them are essential for everyday programming.

Common functions

  1. print(): Prints to the console.
   print("Hello, World!")  # Output: Hello, World!
  1. input(): Gets input from the user.
   name = input("Please enter your name: ")
   print(f"Hello, {name}!")
  1. help(): Displays help information for functions or modules.
   help(len)  # Show help for the len function
  1. range(): Generates a range of integers.
   for i in range(5):
       print(i)  # Output: 0, 1, 2, 3, 4

Summary

Python’s built-in functions are classified by their use, and each provides functionality suited to specific purposes. Understanding them by function in this way makes it intuitive to know which function to use when writing programs. The next section explains tips for learning these built-in functions efficiently and using them in practice.

4. Tips for Learning Python’s Built-in Functions

Python has many built-in functions, and memorizing them all at once can be difficult. However, by using focused and efficient study methods you can quickly learn the functions you need and apply them in practice. This section introduces concrete tips for effectively learning Python’s built-in functions.

Start with Frequently Used Functions

Among the built-in functions, some are used frequently and others less so. At first, we recommend focusing on functions you’ll use most often in everyday coding.

Examples of Commonly Used Functions

  1. print(): Frequently used for program output and debugging.
   print("I started learning Python!")
  1. len(): Get the number of elements in a sequence (list, string, etc.).
   my_list = [1, 2, 3, 4]
   print(len(my_list))  # Output: 4
  1. input(): Get input from the user.
   name = input("Please enter your name: ")
   print(f"Hello, {name}!")
  1. int() / str(): Convert data types.
   age = int(input("Please enter your age: "))
   print(f"Your age is {age}.")
Mastering these basic functions will give you a solid foundation in Python programming.

Use the Official Documentation

Python’s official documentation is the most reliable source for information about built-in functions. Use it effectively with the following steps.
  1. Search for Functions
  1. Try Examples
  • Run the sample code shown in the documentation.
  • Practice by thinking about how to apply it to your own programs to deepen your understanding.
  1. Clear Up Questions
  • If you have questions about how a built-in function behaves, you can use the help() function to check it on the spot.
   help(len)  # Display the description of the len function

Write Code Yourself

The best way to learn built-in functions is by writing programs yourself. Working on simple exercises like the ones below helps you naturally learn how to use the functions.

Sample Exercises

  1. List Operations
  • Retrieve and display the maximum and minimum values in a list.
   numbers = [5, 12, 8, 3]
   print(max(numbers))  # Output: 12
   print(min(numbers))  # Output: 3
  1. Reverse a String
  • Reverse the input string and display it.
   text = input("Please enter a string: ")
   print("Reversed: ", text[::-1])
  1. Data Type Conversion
  • Convert numbers to strings and concatenate them.
   num1 = 10
   num2 = 20
   result = str(num1) + " and " + str(num2)
   print("Concatenation result: ", result)

Use Online Resources

Using online resources helpful for learning Python lets you efficiently master built-in functions.

Recommended Resources

  1. Tutorial Sites
  • Codecademy and the official Python.org tutorials.
  • Interactive exercises let you learn function usage experientially.
  1. Q&A Sites
  • Refer to other programmers’ questions and solutions on forums like Stack Overflow and Qiita.
  1. YouTube Videos
  • Watch beginner-friendly Python tutorial videos and learn by following along.

Build Small Projects

Creating practical projects increases your ability to apply built-in functions.

Project Examples

  1. Simple Calculator
  • Create a program that uses input() to get numbers and performs operations such as +, -, *, and /.
  1. String Counter
  • A program that measures the length of a user-entered string and counts the characters used.
  1. Number Sorting
  • A program that sorts numbers in a list using sorted() and displays both ascending and descending order.

Summary

To efficiently learn Python’s built-in functions, start with frequently used ones and actively make use of the official documentation and online resources. Also, writing programs yourself helps the usage of functions sink in naturally. The next section summarizes what we’ve covered and provides advice to help your future learning.
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5. Summary

Python’s built-in functions are essential tools for improving program efficiency and readability. In this article, we explained in detail the basic concepts of built-in functions, their concrete usage, and efficient ways to learn them.

Key takeaways

  1. Overview and features of built-in functions
  • Functions available out of the box with Python that don’t require additional modules.
  • Convenient tools for simplifying operations and reducing the amount of code you need to write.
  1. Categories of built-in functions
  • Numeric operation functions: abs(), round(), max(), etc., useful for numeric processing.
  • Sequence operation functions: len(), sorted(), zip(), etc., used for list and string operations.
  • Type conversion functions: int(), str(), float(), etc., used for converting data types.
  • Other useful functions: print(), input(), help(), etc., useful for running programs and debugging.
  1. How to learn efficiently
  • Start by learning frequently used functions and make use of the official documentation and online resources.
  • Create small exercises or projects and deepen your understanding by applying built-in functions in practice.

Advice for further learning

After you’ve gone through Python’s built-in functions, moving on to the following topics will help you acquire more advanced programming skills.

User-defined functions

Learn how to define your own functions to implement specific behavior that built-in functions can’t handle.
def greet(name):
    return f"Hello, {name}!"

print(greet("Taro"))

Using the standard library

Python’s standard library includes many utilities beyond built-in functions. Leveraging libraries such as math and datetime will enable even broader programming possibilities.

Using external libraries

Learning external libraries useful for data analysis and machine learning, such as NumPy and Pandas, will enable you to create practical applications.

Object-Oriented Programming (OOP)

By learning Python’s object-oriented features, you’ll gain the skills to create more complex and structured programs.

What you can do with built-in functions

Once you master Python’s built-in functions, you’ll not only be able to run programs, but also gain benefits like the following.
  1. Faster development Many tasks can be implemented easily, allowing you to develop programs more efficiently.
  2. Improved code readability Using built-in functions lets you write code that’s easy to understand.
  3. Increased reliability By using well-tested built-in functions, you can reduce bugs and build more reliable programs.

Finally

By leveraging built-in functions, you can fully bring out Python’s brevity and efficiency. Try applying what you’ve learned in this article to real programs. As you get used to them, you’ll further appreciate the power of built-in functions.
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