Conditional statements let Python choose one path based on a true or false result.
Use if for the first condition, elif for extra choices, and else for the fallback when nothing above matched.
Clear condition logic is about asking one question at a time and making each branch easy to read.
Conditional statements let your program make decisions - executing different code based on whether a condition is True or False. Python uses if, elif, and else.
age = 20
if age >= 18:
print("You are an adult")
print("You can vote")
# Nothing happens if condition is False
temperature = 15
if temperature > 30:
print("It's hot!") # not printedscore = 75
if score >= 60:
print("Pass")
else:
print("Fail")
# Check even or odd
number = 17
if number % 2 == 0:
print(f"{number} is even")
else:
print(f"{number} is odd") # 17 is oddUse elif (short for "else if") to check multiple conditions in sequence.
score = 82
if score >= 90:
grade = "A"
elif score >= 80:
grade = "B"
elif score >= 70:
grade = "C"
elif score >= 60:
grade = "D"
else:
grade = "F"
print(f"Grade: {grade}") # Grade: B
# Multiple conditions with and/or
age = 25
income = 50000
if age >= 18 and income >= 30000:
print("Loan approved")
elif age >= 18 or income >= 50000:
print("Partial approval")
else:
print("Not eligible")num = 15
if num > 0:
print("Positive")
if num % 2 == 0:
print("and even")
else:
print("and odd") # Positive and odd
elif num < 0:
print("Negative")
else:
print("Zero")A one-line shorthand for simple if-else. Syntax: value_if_true if condition else value_if_false
age = 20
status = "adult" if age >= 18 else "minor"
print(status) # adult
# Equivalent to:
# if age >= 18:
# status = "adult"
# else:
# status = "minor"
# In a print statement
x = 42
print("positive" if x > 0 else "non-positive") # positive
# Nested ternary (use sparingly - can hurt readability)
score = 75
grade = "A" if score >= 90 else "B" if score >= 80 else "C" if score >= 70 else "F"
print(grade) # CPython's structural pattern matching - similar to switch/case in other languages but much more powerful.
command = "quit"
match command:
case "quit":
print("Quitting...")
case "help":
print("Showing help")
case "start":
print("Starting...")
case _: # default (wildcard)
print(f"Unknown command: {command}")
# Match with conditions (guards)
point = (0, 5)
match point:
case (0, 0):
print("Origin")
case (x, 0):
print(f"On x-axis at {x}")
case (0, y):
print(f"On y-axis at {y}") # On y-axis at 5
case (x, y):
print(f"Point at ({x}, {y})")In Python, conditions don't have to be explicit True/False. Many values are considered truthy or falsy.
| Falsy Values | Truthy Values |
|---|---|
| False | True |
| None | Any non-zero number |
| 0, 0.0, 0j | Non-empty string |
| - (empty string) | Non-empty list/tuple/set/dict |
| [], (), {}, set() | Any object by default |
name = ""
if name:
print(f"Hello, {name}")
else:
print("Name is empty")
items = []
if items:
print("Has items")
else:
print("Empty list")
result = None
if result is None:
print("No result yet")
username = ""
display = username or "Guest"
print(display)Name is empty
Empty list
No result yet
Guest0 of 2 checked
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Use elif when only one branch should run. Use separate if statements when several independent checks may all run.
No. else is the fallback branch when the preceding if and elif conditions were false.
Use clear boolean names, avoid deeply nested branches, and split complex checks into smaller helper variables.
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