Python Syntax, Comments & Indentation

What is syntax?

Syntax means language ke rules jinke according valid code likha jata hai. Python parser code ko read karke decide karta hai ki structure valid hai ya nahi.

Python statements

A statement is an instruction that Python executes.

course = "Python"
print(course)
print("Keep practicing")

Yahan assignment aur two print() calls separate statements hain.

Try it Yourself →

One statement per line

Beginner code me ek statement per line sabse readable approach hai.

name = "Broun"
city = "Lakhimpur"
print(name, city)

Python semicolon se multiple simple statements same line par allow karta hai, but normal application code me readability ke liye generally avoid karo.

name = "Broun"; city = "Lakhimpur"; print(name, city)

Code blocks and indentation

Python braces { } ke instead indentation se blocks define karta hai.

score = 82

if score >= 60:
    print("Passed")
    print("Good work")

print("Result checked")

Indented two lines if block ke andar hain. Last line block ke bahar hai.

Try indentation →

Use 4 spaces per indentation level

Python style convention commonly 4 spaces per indentation level use karti hai.

logged_in = True
is_admin = True

if logged_in:
    print("Welcome")
    if is_admin:
        print("Admin tools enabled")

Tabs and spaces

Editor settings ko spaces par rakhna safest beginner choice hai. Tabs aur spaces ko inconsistent way me mix karne se TabError ya confusing alignment problems aa sakti hain.

IndentationError

Required block ko indent na karna invalid syntax hai.

age = 20

if age >= 18:
print("Adult")

Python expected an indented block after the if line.

Colon starts many compound blocks

if, for, while, def, class, try jaise compound statements me header ke end par colon commonly required hota hai.

temperature = 31

if temperature > 30:
    print("Hot day")

Colon bhoolne par SyntaxError mil sakta hai.

Single-line comments

# se comment start hota hai. Python us line ke remaining comment text ko normal executable statement nahi maanta.

# Course name shown to the learner
course = "Python"

print(course)  # show current course

Try comments →

Write useful comments

Comments ko obvious code translate karne ke liye nahi, reasoning ya non-obvious intent explain karne ke liye use karo.

# Weak: add 1 to attempts
attempts = attempts + 1

# Better: count this failed login toward the retry limit
attempts = attempts + 1

Python has no special multi-line comment token

Multiple comment lines ke liye each line par # use karna clear approach hai.

# Load learner settings.
# Keep defaults when optional values are missing.
# Validate before displaying the dashboard.

Triple-quoted strings are not automatically comments

Triple quotes se multi-line string literal banta hai. Function, class or module ke first statement ke रूप me use hone par it can act as a docstring, which is runtime metadata — comment nahi.

def greet():
    """Return a short greeting for the learner."""
    return "Hello"

print(greet())

Blank lines improve readability

Related statements ko group karo and logical sections ke beech blank lines use karo.

course = "Python"
chapter = 2

message = f"{course} chapter {chapter}"
print(message)

Long expressions: prefer implicit continuation

Parentheses, brackets aur braces ke andar expressions naturally multiple lines me continue ho sakti hain.

total = (
    120
    + 80
    + 50
)

print(total)

Ye style long expressions ke liye explicit backslash se generally safer/readable hoti hai.

Explicit backslash continuation

Backslash \ se line explicitly continue ki ja sakti hai, but trailing spaces ya edits ise fragile bana sakte hain.

total = 120 + \
        80 + \
        50

Quotes and strings

Single quotes aur double quotes dono string literals ke liye use ho sakte hain.

first = 'Python'
second = "BrounStack"

print(first, second)

Opening quote ko matching closing quote chahiye.

Python is case-sensitive

print and Print same name nahi hain. Keywords and built-ins ko exact case me use karo.

print("works")
# Print("fails unless you defined Print yourself")

Reserved keywords

Python keywords language grammar ka part hain, so unhe normal variable name ke रूप me use nahi kar sakte.

import keyword
print(keyword.kwlist)

if, for, class, def, return jaise words examples hain. Exact keyword list Python version ke saath evolve ho sakti hai.

SyntaxError vs IndentationError

• SyntaxError: grammar invalid — e.g. missing colon, unclosed bracket.
• IndentationError: indentation structure invalid.
• TabError: tabs/spaces inconsistent in a way Python cannot resolve safely.

Readable style and PEP 8

PEP 8 Python code style guide hai. Beginner ke liye key habits: 4-space indentation, sensible blank lines, readable line lengths, spaces around many operators, and clear naming.

# Less readable
result=10+20

# Clearer
result = 10 + 20

Style correctness ka replacement nahi hai, but consistent style code ko easier to read and review banati hai.

Common beginner mistakes

• Block header ke end me colon bhoolna.
• Required block ko indent na karna.
• Same block me inconsistent indentation use karna.
• Tabs aur spaces mix karna.
• Print() likhna instead of print().
• Quotes ya brackets close na karna.
• Triple-quoted strings ko har context me comments samajhna.
• One line me unnecessary semicolons use karna.
• Backslash continuation ko overuse karna.
• Error line ko read kiye bina random edits karna.

Beginner best practices

• 4 spaces per indentation level use karo.
• One statement per line rakho.
• Comments me intent explain karo.
• Parentheses-based continuation prefer karo.
• Logical sections ke beech blank lines use karo.
• Error messages ko first debugging clue samjho.
• Code ko Playground me modify karke indentation experiments karo.

Chapter checklist

• Syntax ka meaning clear hai?
• Statement aur code block ka basic difference samajh aaya?
• Indentation Python me structural kyun hai?
• 4-space convention samajh aayi?
• # comments likh sakte ho?
• Triple-quoted string aur comment ka difference clear hai?
• Colon ka role compound statements me samajh aaya?
• Implicit line continuation use kar sakte ho?
• SyntaxError aur IndentationError ko identify kar sakte ho?