If Statements Explained for Beginners

An if statement lets your program decide. It checks whether something is true, and only runs a block of code when it is.

temperature = 35

if temperature > 30:
    print("It is hot today.")

If the temperature is above 30, the message prints. If not, that line is skipped entirely and the program carries on.

Conditions are just questions with yes/no answers#

Everything inside an if boils down to a true or false value — a boolean. You can print one directly to see it:

print(10 > 3)     # True
print(10 == 3)    # False
print("a" == "a") # True

The comparison operators you will use constantly:

Adding an alternative with else#

else covers every case the if did not.

age = 15

if age >= 18:
    print("You can vote.")
else:
    print("Not yet — come back later.")

Exactly one of those two blocks runs. Never both, never neither.

More than two paths#

Use elif in Python (else if in JavaScript) to chain options. The first matching branch wins and the rest are skipped.

score = 74

if score >= 90:
    grade = "A"
elif score >= 75:
    grade = "B"
elif score >= 60:
    grade = "C"
else:
    grade = "Needs work"

print(grade)   # C

Order matters. If you put score >= 60 first, a score of 95 would match it and stop there, and nobody would ever get an A.

The same thing in JavaScript:

let grade;

if (score >= 90) {
  grade = "A";
} else if (score >= 75) {
  grade = "B";
} else {
  grade = "Needs work";
}

Combining conditions#

• and — both must be true
• or — at least one must be true
• not — flips true and false

age = 22
has_ticket = True

if age >= 18 and has_ticket:
    print("Come in.")

if not has_ticket:
    print("You need a ticket.")

JavaScript uses &&, || and ! for the same three ideas.

Indentation and braces#

Python decides what belongs inside the if purely by indentation. This is why misaligned spaces cause IndentationError.

if logged_in:
    print("Welcome")     # inside the if
print("Goodbye")         # always runs

JavaScript uses braces instead, and ignores your spacing. Omitting the braces around a single statement is legal but a classic source of bugs, so most teams always use them.

A worked example#

password = input("Enter your password: ")

if len(password) < 8:
    print("Too short — use at least 8 characters.")
elif password.isdigit():
    print("Numbers only is easy to guess. Add letters.")
elif password.lower() == "password":
    print("Please, no.")
else:
    print("That will do.")

Notice the checks run cheapest-and-most-likely first. That is a habit worth building.

Where to go next#

• Loops explained — repeating work without repeating yourself
• Python if/else in more depth