Python is one of the most widely-used and popular programming languages, was developed by Guido van Rossum and released first in 1991. Python is a free and open-source language with a very simple and clean syntax which makes it easy for developers to learn Python. It supports object-oriented programming and is most commonly used to perform general-purpose programming. Python is used in several domains like Data Science, Machine Learning, Deep Learning, Artificial Intelligence, Scientific Computing Scripting, Networking, Game Development Web Development, Web Scraping, and various other domains.
To give a comprehensive overview of Python programming, we made a Python Cheat Sheet for Python programmers. In this Cheat Sheet of Python, you’ll learn all the basic to advanced topics and concepts of Python, like Python data types, Python for loop, Python slice, python map function, python dictionary, Python File Handling, etc.
Data Type in Python
The type() function can be used to define the values of various data types and to check their data types.
Python3
# DataType Output: strx = "Hello World" # DataType Output: intx = 50 # DataType Output: floatx = 60.5 # DataType Output: complexx = 3j # DataType Output: listx = ["Lazyroar", "for", "Lazyroar"] # DataType Output: tuplex = ("Lazyroar", "for", "Lazyroar") # DataType Output: rangex = range(10) # DataType Output: dictx = {"name": "Suraj", "age": 24} # DataType Output: setx = {"Lazyroar", "for", "Lazyroar"} # DataType Output: frozensetx = frozenset({"Lazyroar", "for", "Lazyroar"}) # DataType Output: boolx = True # DataType Output: bytesx = b"Geeks" # DataType Output: bytearrayx = bytearray(4) # DataType Output: memoryviewx = memoryview(bytes(6)) # DataType Output: NoneTypex = None |
Python Program to Print Hello world
The print() function in Python is used to print Python objects as strings as standard output.
Python3
# python program to print "Hello World"print("Hello World") |
Output:
Hello World
Python end parameter in print()
The keyword end can be used to avoid the new line after the output or end the output with a different string.
Python3
# ends the output with a spaceprint("Welcome to", end=' ')print("Lazyroar", end=' ') |
Output:
Welcome to Lazyroar
Python sep parameter in print()
The separator between the inputs to the print() method in Python is by default a space, however, this can be changed to any character, integer, or string of our choice. The ‘sep’ argument is used to do the same thing.
Python3
# code for disabling the softspace featureprint('09', '12', '2016', sep='-') # another exampleprint('Example', 'neveropen', sep='@') |
Output:
09-12-2016
Example@neveropen
Python Input
The input() method in Python is used to accept user input. By default, it returns the user input as a string. By default, the input() function accepts user input as a string.
Python3
# Python program showing# a use of input() val = input("Enter your value: ")print(val) |
Output:
Enter your value: Hello Geeks
Hello Geeks
Python Comment
Comments in Python are the lines in the code that are ignored by the interpreter during the execution of the program. There are three types of comments in Python:
- Single line Comments
- Multiline Comments
- Docstring Comments
Python3
# Single Line comment # Python program to demonstrate# multiline comments """ Python program to demonstrate multiline comments""" name = "neveropen"print(name) |
Output:
neveropen
Operators in Python
In general, Operators are used to execute operations on values and variables. These are standard symbols used in logical and mathematical processes.
Arithmetic Operators
Python Arithmetic Operators are used to perform mathematical operations like addition, subtraction, multiplication, and division.
Python3
# Examples of Arithmetic Operatora = 9b = 4 # Addition of numbersadd = a + b # Subtraction of numberssub = a - b # Multiplication of numbermul = a * b # Modulo of both numbermod = a % b # Powerp = a ** b # print resultsprint(add)print(sub)print(mul)print(mod)print(p) |
Output:
13
5
36
1
6561
Comparison Operators
When comparing values, relational operators are utilized. Depending on the criteria, it returns True or False. Comparison Operators are another name for these operators.
Python3
# Examples of Relational Operatorsa = 13b = 33 # a > b is Falseprint(a > b) # a < b is Trueprint(a < b) # a == b is Falseprint(a == b) # a != b is Trueprint(a != b) # a >= b is Falseprint(a >= b) # a <= b is Trueprint(a <= b) |
Output:
False
True
False
True
False
True
Logical Operators in Python
Logical operators are used on conditional statements in Python (either True or False). They conduct the logical AND, OR, and NOT operations.
Python3
# Examples of Logical Operatora = Trueb = False # Print a and b is Falseprint(a and b) # Print a or b is Trueprint(a or b) # Print not a is Falseprint(not a) |
Output:
False
True
False
Bitwise Operators in Python
Bitwise operators are used in Python to do bitwise operations on integers. After converting the numbers to binary, operations are done on each bit or corresponding pair of bits, hence the name bitwise operators.
Python3
# Examples of Bitwise operatorsa = 10b = 4 # Print bitwise AND operationprint(a & b) # Print bitwise OR operationprint(a | b) # Print bitwise NOT operationprint(~a) # print bitwise XOR operationprint(a ^ b) # print bitwise right shift operationprint(a >> 2) # print bitwise left shift operationprint(a << 2) |
Output:
0
14
-11
14
2
40
String Slicing
Strings in Python can be constructed with single, double, or even triple quotes. The slicing method is used to access a single character or a range of characters in a String. A Slicing operator (colon) is used to slice a String.
Python3
# Creating a StringString1 = "GeeksForGeeks"print("Initial String: ")print(String1) # Printing 3rd characterprint("\nSlicing characters from 3-12: ")print(String1[3]) # Printing characters between# 3rd and 2nd last characterprint("\nSlicing characters between " + "3rd and 2nd last character: ")print(String1[3:-2]) |
Output:
Initial String:
GeeksForGeeks
Slicing characters from 3-12:
k
Slicing characters between 3rd and 2nd last character:
ksForGee
Conditional Statements
Decision-making statements in programming languages decide the direction(Control Flow) of the flow of program execution.
Python If-Else
In a conditional if Statement the additional block of code is merged as an else statement which is performed when if condition is false.
Python3
# python program to illustrate If else statement i = 20if (i < 15): print("i is smaller than 15")else: print("i is greater than 15")print("i'm not in if and not in else Block") |
Output:
i is greater than 15
i'm not in if and not in else Block
Python For Loop
The Python For loop is used for sequential traversal, that is, iterating over an iterable such as a String, Tuple, List, Set, or Dictionary. For loops in Python only support collection-based iteration.
Python3
# Python program to illustrate# Iterating over a listl = ["Lazyroar", "for", "Lazyroar"] for i in l: print(i) |
Output:
Lazyroar
for
Lazyroar
Python While Loop
The Python while Loop is used to execute a set of statements repeatedly until a condition is met. When the condition is met, the line immediately following the loop in the program is run.
Python3
# Python program to illustrate# while loopcount = 0while (count < 3): count = count + 1 print("Hello Geek") |
Output:
Hello Geek
Hello Geek
Hello Geek
You can also read the use of break, continue, and pass in Python.
List in Python
The Python list is a sequence data type that is used to store the collection of data. Tuples and String are other types of sequence data types.
Python3
Var = ["Geeks", "for", "Geeks"]print(Var) |
Output:
['Geeks', 'for', 'Geeks']
List comprehension
A Python list comprehension is made up of brackets carrying the expression, which is run for each element, as well as the for loop, which is used to iterate over the Python list’s elements.
Also, Read – Python Array
Python3
# Using list comprehension to iterate through loopList = [character for character in [1, 2, 3]] # Displaying listprint(List) |
Dictionary in Python
A dictionary in Python is a collection of key values, used to store data values like a map, which, unlike other data types holds only a single value as an element.
Python3
Dict = {1: 'Geeks', 2: 'For', 3: 'Geeks'}print(Dict) |
Output:
{1: 'Geeks', 2: 'For', 3: 'Geeks'}
Python Dictionary Comprehension
Like List Comprehension, Python allows dictionary comprehension. We can create dictionaries using simple expressions. A dictionary comprehension takes the form {key: value for (key, value) in iterable}
Python3
# Lists to represent keys and valueskeys = ['a','b','c','d','e']values = [1,2,3,4,5] # but this line shows dict comprehension heremyDict = { k:v for (k,v) in zip(keys, values)} # We can use below too# myDict = dict(zip(keys, values)) print (myDict) |
Output:
{'a': 1, 'b': 2, 'c': 3, 'd': 4, 'e': 5}
Tuples in Python
Tuple is a list-like collection of Python objects. A tuple stores a succession of values of any kind, which are indexed by integers.
Python3
var = ("Geeks", "for", "Geeks")print(var) |
Output:
('Geeks', 'for', 'Geeks')
Sets in Python
Python Set is an unordered collection of data types that can be iterated, mutated and contains no duplicate elements. The order of the elements in a set is unknown, yet it may contain several elements.
Python3
var = {"Geeks", "for", "Geeks"}print(var) |
Output:
{'for', 'Geeks'}
Python Functions
Python Functions are a collection of statements that serve a specific purpose. The idea is to bring together some often or repeatedly performed actions and construct a function so that we can reuse the code included in it rather than writing the same code for different inputs over and over.
Python3
# A simple Python functiondef fun(): print("Welcome to GFG") # Driver code to call a functionfun() |
Output:
Welcome to GFG
Function Arguments
Arguments are the values given between the function’s parenthesis. A function can take as many parameters as it wants, separated by commas.
Python3
# A simple Python function to check# whether x is even or odddef evenOdd(x): if (x % 2 == 0): print("even") else: print("odd") # Driver code to call the functionevenOdd(2)evenOdd(3) |
Output:
even
odd
Return Statement in Python Function
The function return statement is used to terminate a function and return to the function caller with the provided value or data item.
Python3
# Python program to# demonstrate return statementdef add(a, b): # returning sum of a and b return a + b def is_true(a): # returning boolean of a return bool(a) # calling functionres = add(2, 3)print("Result of add function is {}".format(res)) res = is_true(2<5)print("\nResult of is_true function is {}".format(res)) |
Output:
Result of add function is 5
Result of is_true function is True
The range() function
The Python range() function returns a sequence of numbers, in a given range.
Python3
# print first 5 integers# using python range() functionfor i in range(5): print(i, end=" ")print() |
Output:
0 1 2 3 4
Python Map Function
The map() function returns a map object(which is an iterator) of the results after applying the given function to each item of a given iterable.
Python3
# Return double of ndef addition(n): return n + n # We double all numbers using map()numbers = (1, 2, 3, 4)result = map(addition, numbers)print(list(result)) |
Output:
[2, 4, 6, 8]
Python Filter Function
The filter() method filters the given sequence using a function that examines each element in the sequence to see if it is true or false.
Python3
# function that filters vowelsdef fun(variable): letters = ['a', 'e', 'i', 'o', 'u'] if (variable in letters): return True else: return False # sequencesequence = ['g', 'e', 'e', 'j', 'k', 's', 'p', 'r'] # using filter functionfiltered = filter(fun, sequence) print('The filtered letters are:')for s in filtered: print(s) |
Output:
The filtered letters are:
e
e
Python Reduce Function
The reduce function is used to apply a certain function to all of the list components indicated in the sequence sent along.
Python3
from functools import reduce nums = [1, 2, 3, 4]ans = reduce(lambda x, y: x + y, nums)print(ans) |
Output:
10
Python Lambda
Python Lambda Functions are anonymous, which means they have no name. As we already know, the def keyword is used to define a normal function in Python. The lambda keyword in Python is used to declare an anonymous function.
Python3
calc = lambda num: "Even number" if num % 2 == 0 else "Odd number" print(calc(20)) |
Output:
Even number
*args and **kwargs in Python
The *args and **kwargs keywords allow functions to take variable-length parameters. The number of non-keyworded arguments and the action that can be performed on the tuple are specified by the *args.**kwargs, on the other hand, pass a variable number of keyword arguments dictionary to function, which can then do dictionary operations.
Python3
def myFun(arg1, arg2, arg3): print("arg1:", arg1) print("arg2:", arg2) print("arg3:", arg3) # Now we can use *args or **kwargs to# pass arguments to this function :args = ("Geeks", "for", "Geeks")myFun(*args) kwargs = {"arg1": "Geeks", "arg2": "for", "arg3": "Geeks"}myFun(**kwargs) |
Output:
arg1: Geeks
arg2: for
arg3: Geeks
arg1: Geeks
arg2: for
arg3: Geeks
Try and Except Statement
In Python, Try and except statements are used to catch and manage exceptions. Statements that can raise exceptions are kept inside the try clause and the statements that handle the exception are written inside except clause.
Python3
a = [1, 2, 3]try: print ("Second element = %d" %(a[1])) # Throws error since there are only 3 elements in array print ("Fourth element = %d" %(a[3])) except: print ("An error occurred") |
Output:
Second element = 2
An error occurred
File Handling in Python
Python too supports file handling and allows users to handle files i.e., to read and write files, along with many other file handling options, to operate on files.
Python3
import os def create_file(filename): try: with open(filename, 'w') as f: f.write('Hello, world!\n') print("File " + filename + " created successfully.") except IOError: print("Error: could not create file " + filename) def read_file(filename): try: with open(filename, 'r') as f: contents = f.read() print(contents) except IOError: print("Error: could not read file " + filename) def append_file(filename, text): try: with open(filename, 'a') as f: f.write(text) print("Text appended to file " + filename + " successfully.") except IOError: print("Error: could not append to file " + filename) def rename_file(filename, new_filename): try: os.rename(filename, new_filename) print("File " + filename + " renamed to " + new_filename + " successfully.") except IOError: print("Error: could not rename file " + filename) def delete_file(filename): try: os.remove(filename) print("File " + filename + " deleted successfully.") except IOError: print("Error: could not delete file " + filename) if __name__ == '__main__': filename = "example.txt" new_filename = "new_example.txt" create_file(filename) read_file(filename) append_file(filename, "This is some additional text.\n") read_file(filename) rename_file(filename, new_filename) read_file(new_filename) delete_file(new_filename) |
Python OOPs Concepts
Object-oriented Programming (OOPs) is a programming paradigm in Python that employs objects and classes. It seeks to include real-world entities such as inheritance, polymorphisms, encapsulation, and so on into programming. The primary idea behind OOPs is to join the data and the functions that act on it as a single unit so that no other portion of the code can access it.
In this example, we have a Car class with characteristics that represent the car’s make, model, and year. The _make attribute is protected with a single underscore _. The __model attribute is marked as private with two underscores __. The year attribute is open to the public.
We can use the getter function get_make() to retrieve the protected attribute _make. We can use the setter method set_model() to edit the private attribute __model. Using the getter method get_model(), we may retrieve the changed private attribute __model. There are no restrictions on accessing the public attribute year. We manage the visibility and accessibility of class members by using encapsulation with private and protected properties, offering a level of data hiding and abstraction.
Python3
class Car: def __init__(self, make, model, year): self._make = make # protected attribute self.__model = model # private attribute self.year = year # public attribute def get_make(self): return self._make def set_model(self, model): self.__model = model def get_model(self): return self.__model my_car = Car("Toyota", "Corolla", 2022) print(my_car.get_make()) # Accessing protected attributemy_car.set_model("Camry") # Modifying private attributeprint(my_car.get_model()) # Accessing modified private attributeprint(my_car.year) # Accessing public attribute |
Output:
Toyota
Camry
2022
Python RegEx
We define a pattern using a regular expression to match email addresses. The pattern r”\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,}\b” is a common pattern for matching email addresses. Using the re.search() function, the pattern is then found in the given text. If a match is found, we use the match object’s group() method to extract and print the matched email. Otherwise, a message indicating that no email was found is displayed.
Python3
import re # Text to searchtext = "Hello, my email is example@example.com" # Define a pattern to match email addressespattern = r"\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,}\b" # Search for the pattern in the textmatch = re.search(pattern, text) # Check if a match is foundif match: email = match.group() print("Found email:", email)else: print("No email found.") |
Output:
Found email: example@example.com
To learn more about Python, you can follow the Python Tutorial
FAQs on Python
Q.1 What are the key features of Python?
Answer:
Features of Python are includes readability, simplicity, extensive library support, cross-platform compatibility, dynamic typing, a strong community, and object-oriented programming (OOP).
Q.2 What type of language is Python? Programming or scripting?
Answer:
Python is capable of scripting, but in a general sense, it is considered a general-purpose programming language.
Q.3 What is PEP 8?
Answer:
PEP stands for Python Enhancement Proposal. It is a set of rules that specify how to format Python code for maximum readability.
Q.4 What is the difference between .py and .pyc files?
Answer:
The .py files are the python source code files and the .pyc files contain the bytecode of the python files. .pyc files are generated when the code is imported from some other source. The interpreter converts the source .py files to .pyc files which helps by saving time.
