Python Syntax

Python Syntax - A Beginner's Guide

Python syntax is simple and easy to understand, making it a great choice for beginners. Let's go through the basics of Python syntax with examples.

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1. Writing and Running Python Code

Python files have a .py extension. You can run a Python script using:

python script.py

Or use the Python interpreter to execute code line by line.

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2. Python Indentation (No Braces {})

Python uses indentation (spaces/tabs) to define blocks of code instead of curly brackets {}.

✅ Correct indentation:

if True:
    print("Hello, Python!")  # Indented code belongs to the if statement

❌ Incorrect indentation (will cause an error):

if True:
print("Hello, Python!")  # IndentationError: expected an indented block

✅ Python recommends using 4 spaces per indentation level.

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3. Python Comments

Comments make code more readable. Python supports:

(a) Single-line Comments (#)

# This is a comment
print("Hello, World!")  # Output: Hello, World!

(b) Multi-line Comments (""" """ or ''' ''')

"""
This is a 
multi-line comment
"""
print("Python is easy!")

✅ Use comments to explain complex code!

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4. Python Variables and Assignment

Python does not require variable declarations.

x = 10       # Integer
y = "Hello"  # String
z = 3.14     # Float
print(x, y, z)

✅ Python is dynamically typed; variable types are determined at runtime.

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5. Printing Output (print())

name = "Alice"
print("Hello,", name)  # Output: Hello, Alice

✅ Use f-strings for better formatting (Python 3.6+):

age = 25
print(f"My age is {age}")  # Output: My age is 25

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6. Getting User Input (input())

name = input("Enter your name: ")
print("Hello,", name)

✅ By default, input() returns a string. Convert it if needed:

age = int(input("Enter your age: "))  # Converts input to an integer
print("Next year, you'll be", age + 1)

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7. Python Data Types

Python supports various data types:

✅ Use type() to check the data type:

x = 10
print(type(x))  # Output: <class 'int'>

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8. Python Operators

Python supports various operators:

(a) Arithmetic Operators

a = 10
b = 5
print(a + b)  # Addition: 15
print(a - b)  # Subtraction: 5
print(a * b)  # Multiplication: 50
print(a / b)  # Division: 2.0
print(a // b) # Floor Division: 2
print(a % b)  # Modulus: 0
print(a ** b) # Exponentiation: 100000

(b) Comparison Operators

print(10 > 5)  # True
print(10 == 5)  # False
print(10 != 5)  # True

(c) Logical Operators (and, or, not)

x = True
y = False
print(x and y)  # False
print(x or y)   # True
print(not x)    # False

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9. Python Conditional Statements (if, elif, else)

age = 18

if age >= 18:
    print("You are an adult.")
elif age == 17:
    print("Almost an adult.")
else:
    print("You are a minor.")

✅ Indentation is required in conditional statements!

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10. Python Loops (for, while)

(a) for Loop

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

(b) while Loop

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

✅ Use break to exit a loop and continue to skip an iteration.

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11. Python Functions

Functions help in code reusability.

def greet(name):
    print(f"Hello, {name}!")

greet("Alice")  # Output: Hello, Alice!

✅ Functions make code modular and easy to debug.

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12. Python Lists

Lists store multiple items in a single variable.

fruits = ["apple", "banana", "cherry"]
print(fruits[0])  # Output: apple
fruits.append("orange")  # Add an element
print(fruits)

✅ Lists are mutable (modifiable).

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13. Python Tuples

Tuples are immutable (cannot be modified).

coordinates = (10, 20)
print(coordinates[0])  # Output: 10

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14. Python Dictionaries (dict)

Dictionaries store key-value pairs.

person = {"name": "Alice", "age": 25}
print(person["name"])  # Output: Alice
person["city"] = "New York"  # Add new key-value pair
print(person)

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15. Python File Handling

Reading and writing files:

(a) Writing to a File

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

(b) Reading a File

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

✅ Use with open() to avoid closing files manually.

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16. Exception Handling (try-except)

Handle errors gracefully:

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

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Conclusion

• Python uses indentation instead of {} for blocks of code.
• Variables do not require explicit declaration.
• Use if, for, while, def to write logical programs.
• Functions, loops, and exception handling make Python powerful.

🚀 Mastering Python syntax is the first step in becoming a Python expert!

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