Python Basics Cheat Sheet
1. Python Syntax and Structure
Hello World (First Program)
print("Hello, World!")
Variables and Data Types
name = "Alice" # String age = 25 # Integer height = 5.8 # Float is_student = True # Boolean
Comments
# This is a single-line comment """ This is a multi-line comment """
2. Data Structures
Lists
fruits = ["apple", "banana", "cherry"]
fruits.append("orange") # Add item
fruits.remove("banana") # Remove item
print(fruits[0]) # Access first item
Tuples (Immutable Lists)
coordinates = (10, 20) print(coordinates[1]) # Access second item
Dictionaries (Key-Value Pairs)
person = {
"name": "Bob",
"age": 30
}
print(person["name"]) # Access value by key
person["age"] = 31 # Update value
Sets (Unique Values)
unique_numbers = {1, 2, 3, 3, 2}
unique_numbers.add(4)
3. Conditional Statements
age = 18
if age >= 18:
print("Adult")
else:
print("Minor")
Multiple Conditions
score = 85
if score >= 90:
print("Grade A")
elif score >= 75:
print("Grade B")
else:
print("Grade C")
4. Loops
For Loop
for i in range(1, 6):
print(i)
While Loop
count = 0
while count < 5:
print(count)
count += 1
5. Functions
def greet(name):
return f"Hello, {name}!"
print(greet("Alice"))
Default Parameters
def power(base, exponent=2):
return base ** exponent
print(power(3)) # 9
print(power(3, 3)) # 27
6. Classes and Objects
class Dog:
def __init__(self, name):
self.name = name
def bark(self):
return "Woof!"
dog1 = Dog("Rex")
print(dog1.bark())
7. Exception Handling
try:
x = 10 / 0
except ZeroDivisionError:
print("Cannot divide by zero!")
finally:
print("End of operation")
8. File Handling
Read File
with open("example.txt", "r") as file:
content = file.read()
print(content)
Write to File
with open("example.txt", "w") as file:
file.write("Hello, World!")
9. Importing Modules
import math print(math.sqrt(16)) # 4.0
10. List Comprehensions
numbers = [x for x in range(10) if x % 2 == 0] print(numbers) # [0, 2, 4, 6, 8]
11. Useful Built-in Functions
len([1, 2, 3]) # Length of list max([10, 5, 7]) # Max value min([10, 5, 7]) # Min value sum([1, 2, 3, 4]) # Sum of list sorted([3, 1, 2]) # Sort list
12. Useful Tips
- Use f-strings for easier string formatting:
name = "John"
print(f"My name is {name}")
- Use enumerate() to get index in loops:
for index, value in enumerate(["a", "b", "c"]):
print(index, value)
- Use zip() to iterate over multiple lists:
names = ["Alice", "Bob"]
scores = [90, 80]
for name, score in zip(names, scores):
print(f"{name}: {score}")
This cheat sheet provides a quick overview of Python’s essential features.