🐍 Python📅 Day 6

Conditional Statements in Python

if, elif, else, ternary expression and match-case in Python.

🎯

Learning objectives

→Write branching logic with if / elif / else
→Use the inline ternary expression
→Recognise match-case (Python 3.10+)

💡 Key points

Indentation defines the block — no braces. 4 spaces per level is the convention.
elif is Python's else-if (all one word).
Ternary form: `value_if_true if condition else value_if_false`.
match-case (3.10+) is Python's pattern-matching, richer than a plain switch.

💻 Code examples(4)

#1if / elif / else

python

marks = 72
if marks >= 90:
    grade = "A+"
elif marks >= 75:
    grade = "A"
elif marks >= 60:
    grade = "B"
else:
    grade = "Needs work"

print(grade)

Output

Colons + indentation instead of braces. First true branch runs, others skipped.

#2Ternary expression

python

marks = 65
result = "Pass" if marks >= 40 else "Fail"

a, b = 3, 8
biggest = a if a > b else b

Reads left to right as English. Use for simple assignments; avoid nesting.

#3Truthy checks

python

name = ""
if name:
    print(f"Hi {name}")
else:
    print("No name given")

items = []
if not items:
    print("Empty list")

Empty strings, empty lists, 0, None → falsy. No need to write `if len(items) > 0` — just `if items`.

#4match-case (Python 3.10+)

python

def describe(x):
    match x:
        case 0:
            return "zero"
        case 1 | 2 | 3:
            return "small"
        case int() if x > 100:
            return "big int"
        case _:
            return "other"

print(describe(2))    # small
print(describe(200))  # big int

match compares by structure. `|` matches alternatives, `_` is the default case. Powerful — but plain if-elif is still fine for simple cases.

🎯 Practice

Q1. Rewrite as ternary: if x > 0: sign = 1 else: sign = -1+

sign = 1 if x > 0 else -1

Q2. Does Python have a `switch` keyword?+

No traditional switch. Python 3.10+ has `match`/`case` which is a structural pattern-matching feature, more powerful than switch.

Q3. What's wrong: `if x = 5:` ?+

= is assignment, not comparison. Use == for comparison. Python raises SyntaxError — good.

📝 Notes

Guard clauses

Return early to keep code flat:

def grade(marks):
    if not 0 <= marks <= 100:
        return "Invalid"
    if marks >= 90: return "A+"
    if marks >= 75: return "A"
    if marks >= 60: return "B"
    return "C"

Compact single-line conditions

Legal but avoid for anything non-trivial:

if x > 0: print("positive")

Multi-line form is easier to read and diff.