Python Syntax cheat sheet

Assigning Variables

x = 10        # Integer
y = 3.14      # Float
name = "John" # String
is_valid = True  # Boolean

Data Types

type(10) # <class 'int'> type(3.14) # <class 'float'> type("Hello") # <class 'str'> type(True) # <class 'bool'>

Multiple Assignment

a, b, c = 1, 2, 3
x = y = z = 0  # Assign the same value to multiple variables

Type Conversion

int("10")   # 10
float("3.14")  # 3.14
str(100)    # "100"
bool(0)     # False

Arithmetic Operators

5 + 3   # Addition -> 8
5 - 3   # Subtraction -> 2
5 * 3   # Multiplication -> 15
5 / 3   # Division -> 1.666...
5 // 3  # Floor Division -> 1
5 % 3   # Modulus -> 2
5 ** 3  # Exponentiation -> 125

Comparison Operators

5 == 3  # False
5 != 3  # True
5 > 3   # True
5 < 3   # False
5 >= 3  # True
5 <= 3  # False

Logical Operators

True and False  # False
True or False   # True
not True        # False

Assignment Operators

x = 10
x += 5  # x = x + 5
x -= 2  # x = x - 2
x *= 3  # x = x * 3
x /= 2  # x = x / 2
x %= 4  # x = x % 4

If-Else Statements

x = 10
if x > 5:
    print("x is greater than 5")
elif x == 5:
    print("x is 5")
else:
    print("x is less than 5")

For Loop

for i in range(5):  # 0 to 4
    print(i)

While Loop

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

Loop Control Statements

for i in range(10):
    if i == 5:
        break  # Stops the loop
    if i % 2 == 0:
        continue  # Skips even numbers
    print(i)

Defining Functions

def greet(name):
    return "Hello, " + name

print(greet("Alice"))  # "Hello, Alice"

Default Parameters

def greet(name="User"):
    return "Hello, " + name

print(greet())  # "Hello, User"

Lambda Functions

square = lambda x: x * x
print(square(4))  # 16

Creating and Accessing Lists

fruits = ["apple", "banana", "cherry"]
print(fruits[0])  # "apple"
print(fruits[-1]) # "cherry"

List Methods

fruits.append("orange")  # Add item
fruits.remove("banana")  # Remove item
fruits.pop()  # Remove last item
fruits.sort()  # Sort list

Creating and Accessing Dictionaries

person = {"name": "John", "age": 30}
print(person["name"])  # "John"

Dictionary Methods

person.keys()   # Get all keys
person.values() # Get all values
person.items()  # Get key-value pairs

Creating and Accessing Tuples

colors = ("red", "green", "blue")
print(colors[1])  # "green"

Immutable Nature

# colors[1] = "yellow"  # TypeError: 'tuple' object does not support item assignment

Creating and Using Sets

numbers = {1, 2, 3, 4}
numbers.add(5)
numbers.remove(2)
print(numbers)

String Methods

text = "hello world"
print(text.upper())  # "HELLO WORLD"
print(text.lower())  # "hello world"
print(text.title())  # "Hello World"
print(text.replace("world", "Python"))  # "hello Python"

String Formatting

name = "Alice"
age = 25
print(f"My name is {name} and I am {age} years old.")

Reading a File

with open("file.txt", "r") as file:
    content = file.read()
    print(content)

Writing to a File

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

Try-Except Block

try:
    x = 10 / 0
except ZeroDivisionError:
    print("Cannot divide by zero")

Handling Multiple Exceptions

try:
    num = int(input("Enter a number: "))
    print(10 / num)
except (ValueError, ZeroDivisionError):
    print("Invalid input!")

Useful Tips

• Indentation is crucial in Python. Use 4 spaces per indent.
• Use list comprehensions for concise code:

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

• Use enumerate() to get index-value pairs in loops:

  for index, value in enumerate(["a", "b", "c"]):
  print(index, value)

• Use zip() to iterate over multiple lists:

  names = ["Alice", "Bob"]
  scores = [85, 92]
  for name, score in zip(names, scores):
  print(name, score)

Reliable Sources

• Python Official Documentation
• W3Schools Python Tutorial
• Real Python