Python CheatSheet

Basics

Basic syntax from the Python programming language

Showing Output To User

The print function is used to display or print output as follows:

print("Content that you wanna print on screen")

We can display the content present in an object using the print function as follows:

var1 = "Shruti"
print("Hi my name is: ", var1)

You can also use f-strings for cleaner output formatting:

name = "Shruti"
print(f"Hi my name is: {name}")

Taking Input From the User

The input function is used to take input as a string from the user:

var1 = input("Enter your name: ")
print("My name is: ", var1)

Typecasting allows us to convert input into other data types:

Integer input:

var1 = int(input("Enter the integer value: "))
print(var1)

Float input:

var1 = float(input("Enter the float value: "))
print(var1)

range Function

The range function returns a sequence of numbers, starting from start, up to but not including stop, with a default step of 1:

range(start, stop, step)

Example - display all even numbers between 1 to 100:

for i in range(0, 101, 2):
    print(i)

Comments

Single Line Comment

# This is a single line comment

Multi-line Comment (Docstring Style)

"""This is a
multi-line
comment"""

Escape Sequences

Common escape sequences:

• \n → Newline
• \t → Tab space
• \\ → Backslash
• \' → Single quote
• \" → Double quote
• \r → Carriage return
• \b → Backspace

Example:

print("Hello\nWorld")

Strings

Creation

variable_name = "String Data"

Indexing & Slicing

str = "Shruti"
print(str[0])     # S
print(str[1:4])   # hru
print(str[::-1])  # reverse string

Useful String Methods

• isalnum() → Check alphanumeric
• isalpha() → Check alphabetic
• isdigit() → Check digits
• islower(), isupper() → Check case
• isspace() → Check for whitespace
• lower(), upper() → Convert case
• strip(), lstrip(), rstrip() → Remove spaces
• startswith(), endswith() → Check prefixes/suffixes
• replace(old, new) → Replace substring
• split(delimiter) → Split string
• join(iterable) → Join elements into string

Example:

name = " Shruti "
print(name.strip())

Lists

Creation

my_list = [1, 2, 3, "hello"]

Operations

my_list.append(5)
my_list.insert(1, "new")
my_list.remove("hello")
item = my_list.pop()  # removes last element
my_list.sort()
my_list.reverse()

List Comprehension

squares = [x**2 for x in range(10)]

Tuples

Immutable, ordered collection:

my_tuple = (1, 2, 3)
print(my_tuple.count(2))
print(my_tuple.index(3))

Sets

Unordered, unique elements:

my_set = {1, 2, 3}
my_set.add(4)
my_set.remove(2)
my_set.union({5, 6})

Other useful set methods: intersection(), difference(), symmetric_difference()

Dictionaries

Key-value pairs:

mydict = {"name": "Shruti", "age": 20}
print(mydict["name"])
mydict["age"] = 21
mydict.update({"city": "Delhi"})

Useful methods: keys(), values(), items(), get(), pop(key), clear()

Indentation

Python uses indentation (usually 4 spaces) to define blocks.

Conditional Statements

if x > 0:
    print("Positive")
elif x < 0:
    print("Negative")
else:
    print("Zero")

Loops

For Loop

for i in range(5):
    print(i)

While Loop

i = 0
while i < 5:
    print(i)
    i += 1

Loop Control

• break → exits loop
• continue → skips iteration
• pass → does nothing (placeholder)

Functions

def greet(name):
    return f"Hello {name}"
 
print(greet("Shruti"))

Supports default arguments, keyword arguments, *args, and **kwargs.

File Handling

with open("file.txt", "w") as f:
    f.write("Hello")

Modes: r, w, a, r+, w+, a+

Read methods: read(), readline(), readlines()

Exception Handling

try:
    x = 10 / 0
except ZeroDivisionError as e:
    print("Error:", e)
else:
    print("No error")
finally:
    print("Always runs")

Object Oriented Programming (OOP)

class Person:
    def __init__(self, name):
        self.name = name
    def greet(self):
        print(f"Hello, I am {self.name}")
 
p = Person("Shruti")
p.greet()

Supports inheritance, polymorphism, encapsulation, and abstraction.

Useful Built-in Functions

• len(), type(), id(), dir(), help()
• sum(), max(), min(), sorted()
• enumerate(), zip(), map(), filter(), any(), all()

Modules & Imports

import math
print(math.sqrt(16))
 
from datetime import datetime
print(datetime.now())

Virtual Environments (Best Practice)

python -m venv env
source env/bin/activate  # Linux/Mac
env\Scripts\activate     # Windows

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