A mark of 90 runs through this chain: if marks >= 35: print("C"), elif marks >= 60: print("B"), elif marks >= 80: print("A"). What is printed?

C, because Python stops at the first true branch

A, because 90 is the highest grade

C, because Python stops at the first true branch

C B A, because all three are true

Nothing, because the order is wrong

Why use if / else rather than two separate if statements for pass and fail?

With else there is one condition to keep correct instead of two that must stay opposite

Two if statements run more slowly

else is required whenever there is an if

Two if statements cannot use the same variable

With else there is one condition to keep correct instead of two that must stay opposite

What does result = "Pass" if marks >= 35 do?

Stores None when the marks are below 35

Stores "Pass" only when the marks reach 35, and leaves result unset otherwise

Stores False when the marks are below 35

When is nesting one if inside another the better choice?

Whenever there is more than one condition

When the conditions test different variables

Never — and always reads better

Conditional Statements in Python

By the Syncfusion DevTutorials team · Last updated October 19, 2026

How to run code only when a test is true: if, else, elif chains and why their order matters, nesting, and the one-line conditional expression.

Think about getting ready for school in the morning.

You look outside. If it is raining, you take an umbrella. If it is not, you leave it at home.

You made a decision. You checked something, and what you did next depended on the answer.

Programs make decisions the same way, and the word they use is if.

A program that decides

marks = 78

if marks >= 35:
    print("Passed")

The program checked whether the marks were 35 or more. They were, so it printed Passed.

Change 78 to 20 and run it again. Nothing is printed at all, because the test was false and the indented line was skipped.

What You Will Learn

In this lesson, you will learn:

How to run some code only when a test is true
How to give the program something else to do when the test is false
How to check several conditions in order, and why the order matters
How to put one decision inside another, and when not to
How to choose between two values in a single line

A conditional statement runs a block of code only when a test is true.

Introduction to Conditional Statements

What Is a Conditional Statement?

A conditional statement is a block of code that runs only when a test is true.

The test is called the condition. It is anything that produces True or False.

For example, marks >= 35 is a condition. Python checks it and gets either True or False, and the conditional statement uses that answer to decide what to do next.

Why Conditional Statements Are Used

Without conditions, a program does exactly the same thing every time it runs. It cannot react to anything.

The same thing, every time

marks = 20

print("Result for the term")
print("Marks:", marks)
print("Passed")

That program prints Passed for a mark of 20, which is wrong. It has no way to tell the difference.

With a condition, the program responds to what it is given:

A program that reacts

PASS_MARK = 35
marks = 20

print("Result for the term")
print("Marks:", marks)

if marks >= PASS_MARK:
    print("Passed")

if marks < PASS_MARK:
    print("Failed")

Same program, honest answer. The condition is what makes a program useful rather than a fixed list of instructions. Every useful program — a game, a login check, a marks sheet — has to react to what happens, and this is the tool that lets it.

if Statement

What Is an if Statement?

An if statement runs a block of code when its condition is true, and skips it when the condition is false.

Syntax of if Statement

if condition:
    code that runs when the condition is true

Three parts matter, and leaving any of them out stops the program:

the word if
the condition
a colon : at the end of the line

The lines under it must be indented by four spaces. The indentation is what tells Python which lines belong to the if.

The shape of an if statement

attendance = 92

if attendance >= 75:
    print("Attendance is fine")
    print("No letter needed")

print("Report finished")

Two lines are indented, so both belong to the if. The last line is not indented, so it runs whatever the answer was.

Executing Conditional Code

The condition can be any expression that gives True or False.

Four different conditions

marks = 78
remark = "Good work"

if marks > 75:
    print("Above 75")

if marks != 100:
    print("Not full marks")

if "work" in remark:
    print("The remark mentions work")

if marks:
    print("Marks is not zero")

The first three conditions are comparisons you have met before. The last one is worth a second look. marks is not a comparison, but Python can still read any value as true or false. 78 counts as true, so the line runs. 0 would count as false.

Simple Examples

A decision made from what the user types

attendance = int(input("Attendance percent: "))

if attendance < 75:
    print("Attendance is below the required 75 percent")

print("Checked")

The Input box holds 92, so nothing is printed about attendance. Change it to 60 and run again. The warning appears.

Forgetting the colon is the most common slip here:

A missing colon

marks = 78

if marks >= 35
    print("Passed")

SyntaxError: expected ':' is Python saying the line looked like an if but never finished. The editor marks this one as you type.

if else Statement

What Is an if else Statement?

else gives the program something to do when the condition is false.

if condition:
    code for when the condition is true
else:
    code for when it is false

else has no condition of its own. It catches everything the if did not.

Two paths, one of them always runs

PASS_MARK = 35
marks = 20

if marks >= PASS_MARK:
    print("Passed")
else:
    print("Failed")

Alternative Execution Paths

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

Only one block runs

attendance = 60

if attendance >= 75:
    print("Attendance is fine")
    print("No action needed")
else:
    print("Attendance is low")
    print("A letter will be sent home")

print("Done")

Compare this with the two separate if statements from earlier. Two if statements test twice; an if else tests once and chooses. If the two cases are opposites, else says so more clearly and cannot get out of step.

Using if else Effectively

Write the condition for the case you care about most, and let else handle the rest.

The important case first

marks = 78

if marks >= 75:
    print("Distinction")
else:
    print("No distinction")

Avoid testing the same thing twice in opposite directions:

Testing the same thing twice

marks = 78

if marks >= 35:
    print("Passed")

if marks < 35:
    print("Failed")

This works, but the two conditions have to stay opposite for ever. Change 35 to 40 in one line and not the other, and a mark of 37 prints nothing at all. else cannot drift that way, because there is only one condition to keep correct.

If the second test is the exact opposite of the first, use else. One condition is one thing to keep correct instead of two.

if elif else Statement

Multiple Conditions

elif is short for "else if". It adds another condition to test when the one above was false.

if first condition:
    ...
elif second condition:
    ...
else:
    ...

Turning a mark into a grade

marks = 78

if marks >= 80:
    print("Grade A")
elif marks >= 60:
    print("Grade B")
elif marks >= 35:
    print("Grade C")
else:
    print("Fail")

A mark of 78 is not 80 or more, so the first test failed. It is 60 or more, so the second succeeded and printed Grade B.

You can have as many elif branches as you need. The else at the end is optional.

Decision Chains

The whole chain is one statement, and only one branch ever runs.

Only one branch runs, even when several fit

marks = 90

if marks >= 80:
    print("Grade A")
elif marks >= 60:
    print("Grade B")
elif marks >= 35:
    print("Grade C")

A mark of 90 is 80 or more, 60 or more, and 35 or more. All three conditions are true. Only Grade A printed, because Python stops at the first branch that succeeds.

Condition Evaluation Order

Python reads the branches from the top down and stops at the first true one. That makes the order part of the meaning.

Here is the same chain with the conditions in the wrong order:

The wrong order gives the wrong grade

marks = 90

if marks >= 35:
    print("Grade C")
elif marks >= 60:
    print("Grade B")
elif marks >= 80:
    print("Grade A")

A mark of 90 now prints Grade C. Nothing is broken: 90 really is 35 or more, so the first branch matched and the rest were never read.

The two later branches can never run at all. Every mark that would reach them was already caught by the first.

In an if elif else chain, put the narrowest condition first and the widest last. A wide condition at the top swallows every branch below it, and the program still runs without an error.

Nested Conditions

Nested if Statements

An if can go inside another if. This is called nesting.

The inner test is only reached when the outer one is true.

A test inside a test

marks = 90
attendance = 92

if marks >= 35:
    print("Passed")
    if marks >= 80:
        print("With distinction")

With distinction is indented twice, so it runs only when both tests are true.

Nested if else Statements

A choice inside a choice

marks = 90
attendance = 60

if marks >= 35:
    if attendance >= 75:
        print("Promoted")
    else:
        print("Passed the exam, but attendance is too low")
else:
    print("Failed")

The student passed the exam, so Python went into the first block. Inside it, attendance was below 75, so the else ran.

Best Practices

Nesting works, but every level moves the code further right and makes it harder to follow. Two levels are fine. Four are a sign something should change.

Most nesting can be replaced with and, putting both tests in one condition instead of one inside the other:

The same rule without nesting

marks = 90
attendance = 60

if marks >= 35 and attendance >= 75:
    print("Promoted")
elif marks >= 35:
    print("Passed the exam, but attendance is too low")
else:
    print("Failed")

Same three outcomes, one level of indentation, and the rule reads as a sentence.

Another way to reduce nesting is to deal with the simple case first and get it out of the way:

Handling the simple case first

marks = 20

if marks < 35:
    print("Failed")
else:
    if marks >= 80:
        print("Distinction")
    else:
        print("Passed")

Reach for and before you reach for a second level of indentation. Keep nesting for the cases where the inner question only makes sense once the outer one is answered.

Conditional Expressions

One-Line Conditions

A conditional expression chooses between two values in a single line.

value_if_true if condition else value_if_false

A choice written on one line

PASS_MARK = 35
marks = 78

print("Pass" if marks >= PASS_MARK else "Fail")

Read it as a sentence: "Pass", if the marks reach the pass mark, otherwise "Fail".

Conditional Assignment

The usual use is to store the chosen value in a variable.

Storing the chosen value

PASS_MARK = 35
marks = 20

result = "Pass" if marks >= PASS_MARK else "Fail"

print("Result:", result)

Four lines of if else become one. Both forms are correct, and the right choice depends on how much happens in each branch.

The same thing as a full if else

PASS_MARK = 35
marks = 20

if marks >= PASS_MARK:
    result = "Pass"
else:
    result = "Fail"

print("Result:", result)

A conditional expression must always have its else. Leaving it out is an error, because the expression has to produce a value either way:

A conditional expression with no else

marks = 78

result = "Pass" if marks >= 35

print(result)

They can be chained, but a chain quickly becomes hard to read:

A chain that is already too long

marks = 78

grade = "A" if marks >= 80 else "B" if marks >= 60 else "C" if marks >= 35 else "F"

print(grade)

That line is correct and gives B. An if elif else chain says the same thing in a way anyone can read at a glance. Use the one-line form for a simple either-or, and the full statement for anything longer.

Common mistakes

Each row is one mistake. The middle column is what you will actually see on screen.

Mistake	What you see	Why it happens	Fix
Forgetting the colon	`SyntaxError: expected ':'`	An `if` line must end in `:`	`if marks >= 35:`
Forgetting to indent the block	`IndentationError: expected an indented block`	A `:` promises a block, so the block must be there	Indent the next line by four spaces
Using `=` instead of `==`	`SyntaxError: invalid syntax`	One `=` stores a value; a test needs two	`if marks == 78:`
Widest condition first in a chain	A wrong grade, with no error at all	Python stops at the first true branch	Put the narrowest condition first
Using several `if`s where `else` belongs	Two messages printed, or none	Separate `if`s are tested separately and can drift apart	Use `if` / `else` for opposite cases
A condition that can never be true	A branch that silently never runs	An earlier branch already covers every value	Read the chain from the top and check each branch can be reached
Leaving out `else` in a one-line choice	`SyntaxError: invalid syntax`	A conditional expression must produce a value either way	Add the `else` part
Indenting a line that should run always	A line that only runs sometimes	Indentation decides what belongs to the block	Move it back to the left margin
Comparing text to a number	`TypeError: '>=' not supported`	`input()` hands back text, which cannot be compared to a number	Wrap it in `int()` first

What to Remember

A conditional statement runs a block of code only when a test is true.
An if line ends in a colon, and the block under it is indented by four spaces.
else catches everything the if did not, and needs no condition of its own.
elif adds another condition to try when the ones above were false.
Only one branch of a chain ever runs, and Python stops at the first true one.
Order is part of the meaning: the narrowest condition goes first, the widest last.
A wide condition at the top makes the branches below it unreachable, with no error.
Nesting puts one decision inside another. Prefer and unless the inner question depends on the outer one.
value_if_true if condition else value_if_false chooses between two values in one line, and its else is required.

Next: Pattern Matching