Python is a popular programming language. It was created by Guido van Rossum, and released in 1991.
print("Hello, World!")Python is an interpreted, high-level, general-purpose programming language. Created by Guido van Rossum and first released in 1991, Python's design philosophy emphasizes code readability with its notable use of significant indentation.
Python is often described as a "batteries included" language due to its comprehensive standard library. This means you can do a lot out-of-the-box without needing to install third-party packages. It is widely used in various domains, ranging from web development (using frameworks like Django and Flask) to data science, artificial intelligence, scientific computing, and simple task automation.
Unlike languages like C++ or Java, Python uses whitespace (indentation) to define code blocks (like functions or loops) instead of curly braces. This enforces a clean, consistent coding style across all Python codebases.
# Basic Python syntax
print("Welcome to Python!")
# No semicolons required at the end of the line
name = "LearnX Student"
print(f"Hello, {name}! Let's learn Python.")
A data analyst using Python to load a CSV file and calculate the average sales for a month without complex configuration or compilation steps.
Python can be easily installed on Windows, macOS, and Linux. Once installed, writing and running Python code is remarkably quick.
Modern Python development usually requires Python 3 (Python 2 is officially deprecated). When you install Python on Windows, make sure to check the box that says "Add Python to PATH". This step is crucial for running Python from any command prompt window.
After installation, you can interact with Python in two main ways: using the interactive shell (REPL) or by saving your code in a file with a .py extension and running it.
# Check python version
python --version
# Run a python script
python myscript.py
Python's syntax was uniquely designed to be highly readable. It leverages English keywords where other languages use punctuation, and it uses indentation to define the structure of the code.
Indentation is the most critical aspect of Python syntax. Where other programming languages use indentation purely for readability, Python uses it to indicate a block of code (e.g., the body of a loop, function, or conditional statement). You must use the same number of spaces for every line within the same block, though the standard convention is 4 spaces.
You can write multiple statements on one line by separating them with a semicolon, but this is highly discouraged in Python as it hurts readability.
# Correct indentation
if 5 > 2:
print("Five is greater than two!")
# Incorrect indentation (will cause an error)
# if 5 > 2:
# print("Five is greater than two!")
x = 10
if x == 10:
print("x is 10")
print("This is inside the 'if' block")
print("This is outside the block")
Comments are an essential part of programming. They are used to explain Python code, make the code more readable, and can also be used to prevent execution when testing code blocks.
# symbol.# on every line, or use an unassigned multi-line string.When the Python interpreter encounters a #, it ignores the rest of the line. This means you can write whatever text you want after it, making it perfect for leaving notes for yourself or other developers.
For multi-line comments, you can add a # at the beginning of each line. Alternatively, you can use triple quotes """. Since Python will ignore string literals that are not assigned to a variable, many developers use triple quotes to write extensive documentation or comment out large chunks of code.
# This is a single-line comment
print("Hello, World!") # This is an end-of-line comment
"""
This is a comment
written in
more than just one line
"""
print("Multi-line comments are cool!")
# This is an important calculation
x = 5
y = 10
# print(x + y) <-- This line is commented out and will not run
print("End of program")Variables are containers for storing data values. Unlike other programming languages, Python has no command for declaring a variable.
In Python, you simply assign a value to a variable name using the equals sign =. Under the hood, Python variables act as "labels" pointing to objects in memory rather than fixed buckets. This is why a variable can point to an integer on one line, and a string on the next.
You can also assign multiple variables in one line to keep your code concise (e.g., x, y, z = "Orange", "Banana", "Cherry"). If you want to assign the same value to multiple variables, you can do x = y = z = "Orange".
# Variable assignment
x = 5 # x is an integer
name = "John" # name is a string
x = "Sally" # x is now a string!
# Multiple variables in one line
a, b, c = 1, 2, 3
x = 5
y = "John"
print(x)
print(y)Variables are used to hold the state of an application. For example, a variable `score` keeps track of a player's points in a game, while `player_name` holds their username.
In programming, data type is an important concept. Variables can store data of different types, and different types allow you to perform different operations.
strint, float, complexlist, tuple, rangedictset, frozensetboolbytes, bytearray, memoryviewNoneTypePython variables are strongly but dynamically typed. You don't need to specify the type when declaring the variable, but Python tracks the type of the underlying object. To check the data type of any object, you can use Python's built-in type() function.
If you want to enforce a specific data type, you can use constructor functions like str(), int(), or list().
x = "Hello World" # str
x = 20 # int
x = 20.5 # float
x = ["apple", "ban"] # list
x = {"name" : "Bob"} # dict
x = True # bool
x = 5
y = [1, 2, 3]
print(type(x))
print(type(y))There are three distinct numeric types in Python: int, float, and complex. Variables of numeric types are created when you assign a value to them.
Python supports large numbers out of the box. Unlike C or Java where you have specific limits for `int` (like 32-bit limits), a Python `int` can be as large as your system's memory allows.
You can convert from one type to another with the int(), float(), and complex() methods. However, you cannot convert complex numbers into another number type.
x = 1 # int
y = 2.8 # float
z = 1j # complex
print(type(x))
print(type(y))
print(type(z))Python does not have a `random()` function built-in, but it has a built-in module called `random` that can be used to make random numbers:
import random
print(random.randrange(1, 10))
Casting in python is therefore done using constructor functions:
int() - constructs an integer number from an integer literal, a float literal (by
removing all decimals), or a string literal (providing the string represents a whole number).float() - constructs a float number from an integer literal, a float literal or a string
literal (providing the string represents a float or an integer).str() - constructs a string from a wide variety of data types, including strings, integer
literals and float literals.x = int(1) # x will be 1
y = int(2.8) # y will be 2
z = int("3") # z will be 3Strings in python are surrounded by either single quotation marks, or double quotation marks.
print() function.a = "Hello"
print(a)Booleans represent one of two values: True or False.
True or False.
True or
False.
print(10 > 9)
print(10 == 9)
print(10 < 9)Operators are used to perform operations on variables and values.
print(10 + 5)Lists are used to store multiple items in a single variable.
[].[0].thislist = ["apple", "banana", "cherry"]
print(thislist)Tuples are used to store multiple items in a single variable.
().[0].thistuple = ("apple", "banana", "cherry")
print(thistuple)Sets are used to store multiple items in a single variable.
{}.thisset = {"apple", "banana", "cherry"}
print(thisset)Dictionaries are used to store data values in key:value pairs.
thisdict = {
"brand": "Ford",
"model": "Mustang",
"year": 1964
}
print(thisdict)Python supports the usual logical conditions from mathematics:
a == ba != ba < ba <= ba > ba >= ba = 33
b = 200
if b > a:
print("b is greater than a")With the while loop we can execute a set of statements as long as a condition is true.
while loop requires relevant variables to be ready.i = 1
while i < 6:
print(i)
i += 1A for loop is used for iterating over a sequence (that is either a list, a tuple, a
dictionary, a set, or a string).
for keyword in other programming languages, and works more like an
iterator method as found in other object-orientated programming languages.fruits = ["apple", "banana", "cherry"]
for x in fruits:
print(x)A function is a block of code which only runs when it is called.
def keyword.def my_function():
print("Hello from a function")
my_function()A lambda function is a small anonymous function.
lambda arguments : expressionx = lambda a : a + 10
print(x(5))Consider a module to be the same as a code library. A file containing a set of functions you want to include in your application.
.py.
import statement.import platform
x = platform.system()
print(x)PIP is a package manager for Python packages, or modules if you like.
C:\Users\Your Name\AppData\Local\Programs\Python\Python36-32\Scripts>pip --versionA date in Python is not a data type of its own, but we can import a module named datetime to
work with dates as date objects.
datetime module has many methods to return information about the date object.import datetime
x = datetime.datetime.now()
print(x)Python has a set of built-in math functions, including an extensive math module, that allows you to perform mathematical tasks on numbers.
min() and max(), abs(),
pow().
math module has a set of methods and constants.x = min(5, 10, 25)
y = max(5, 10, 25)
print(x)
print(y)A RegEx, or Regular Expression, is a sequence of characters that forms a search pattern.
re, which can be used to work with Regular
Expressions.import re
txt = "The rain in Spain"
x = re.search("^The.*Spain$", txt)Python does not have built-in support for Arrays, but Python Lists can be used instead.
cars = ["Ford", "Volvo", "BMW"]
print(cars[0])Python is an object oriented programming language.
__init__() function is always executed when the class is being initiated.class MyClass:
x = 5
p1 = MyClass()
print(p1.x)Inheritance allows us to define a class that inherits all the methods and properties from another class.
class Person:
def __init__(self, fname, lname):
self.firstname = fname
self.lastname = lname
class Student(Person):
passFile handling is an important part of any web application.
open() function.open() function takes two parameters; filename, and
mode.
f = open("demofile.txt", "r")
print(f.read())When an error occurs, or exception as we call it, Python will normally stop and generate an error message.
try block lets you test a block of code for errors.except block lets you handle the error.else block lets you execute code when there is no error.finally block lets you execute code, regardless of the result of the try- and except
blocks.try:
print(x)
except:
print("An exception occurred")Python allows for user input. That means we are able to ask the user for input.
input() method.raw_input() method.username = input("Enter username:")
print("Username is: " + username)To make sure a string will display as expected, we can format the result with the format()
method or using f-strings.
f"Hello {name}"format() method allows you to format selected parts of a string.price = 49
txt = f"The price is {price} dollars"
print(txt)Apply your skills with these project ideas.
Goal: Temperature Converter.
celsius = 25.(celsius * 9/5) + 32.JSON is a syntax for storing and exchanging data. JSON is text, written with JavaScript object notation.
json, which can be used to work with JSON data.json.loads(): Parse JSON (convert from JSON to Python).json.dumps(): Convert from Python to JSON.import json
# some JSON:
x = '{ "name":"John", "age":30, "city":"New York"}'
# parse x:
y = json.loads(x)
print(y["age"])An iterator is an object that contains a countable number of values.
__iter__() and __next__().mytuple = ("apple", "banana", "cherry")
myit = iter(mytuple)
print(next(myit))
print(next(myit))The word "polymorphism" means "many forms", and in programming it refers to methods/functions/operators with the same name that can be executed on many objects or types.
len() function, which can be used on different
objects.class Car:
def move(self):
print("Drive!")
class Boat:
def move(self):
print("Sail!")
car1 = Car()
boat1 = Boat()
for x in (car1, boat1):
x.move()A variable is only available from inside the region it is created. This is called scope.
def myfunc():
x = 300 # Local scope
print(x)
myfunc()To open a file for reading it is enough to specify the name of the file.
open() function returns a file object.read() method to read the content of the file.readline() to read one line of the file.f = open("demofile.txt", "r")
print(f.read())To write to an existing file, you must add a parameter to the open() function.
"a" - Append - will append to the end of the file."w" - Write - will overwrite any existing content.f = open("demofile2.txt", "a")
f.write("Now the file has more content!")
f.close()To delete a file, you must import the OS module, and run its os.remove() function.
os.rmdir() method.import os
if os.path.exists("demofile.txt"):
os.remove("demofile.txt")
else:
print("The file does not exist")Test your Python skills with our Quiz!
We have gathered a variety of Python exercises (with answers) for each Python Chapter.
In this tutorial you have learned a lot about Python.
You've completed the Python module.