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Table of Contents
What is if else?
How to use multiple conditions? The role of elif
Indentation is important!
Can it be simplified into one line? Let's learn about the simple writing method
Home Backend Development Python Tutorial what is if else in python

what is if else in python

Jul 13, 2025 am 02:48 AM
python if else

if else is the infrastructure used in Python for conditional judgment, and different code blocks are executed through the authenticity of the condition. It supports the use of elif to add branches when multi-condition judgment, and indentation is the syntax key; for example, when num = 15, the program outputs "this number is greater than 10"; if the assignment logic is required, a ternary operator such as status = "adult" if age >= 18 else "minor". 1. If else selects the execution path according to the true or false conditions; 2. elif can add multiple condition branches; 3. Indentation determines the code's ownership, errors will cause exceptions; 4. The ternary operator is suitable for simple assignment scenarios.

What is if else in python

if else is one of the most basic conditional judgment statements in Python, used to execute different code blocks according to different conditions. It's like a "selector": do one thing if you meet a certain condition, otherwise do another.

What is if else in python

What is if else?

Simply put, the structure of if else is:

 if conditions:
    # Code else executed when the condition is true:
    # Code executed when the condition is false

To give a simple example, for example, you write a program to determine whether a number is greater than 10:

What is if else in python
 num = 15

if num > 10:
    print("This number is greater than 10")
else:
    print("This number is not greater than 10")

The output result is:

 This number is greater than 10

You can see that the program decides which piece of code to execute based on the authenticity of the condition num > 10 .

What is if else in python

How to use multiple conditions? The role of elif

If there are only two cases, use if else is enough. But in reality, there are often situations where multiple situations coexist. At this time, you can use elif (actually the abbreviation of else if) to add more judgment branches.

For example, judging grades:

 score = 85

if score >= 90:
    print("A")
elif score >= 80:
    print("B")
elif score >= 70:
    print("C")
else:
    print("D")

As you can see here, once a certain condition is true, the subsequent elif and else will no longer be judged.


Indentation is important!

In Python, indentation is not for good looking, but part of the syntax. All codes belonging to if or else must be indented uniformly, usually with 4 spaces.

For example, if the following will make an error:

 if True:
print("correct") # If there is no indentation, Python will report an error

The correct way to write it should be:

 if True:
    print("correct")

Therefore, when writing if else , you must pay attention to whether the indentation is aligned, otherwise it is easy to cause logical errors or operation errors.


Can it be simplified into one line? Let's learn about the simple writing method

Sometimes we want to write it shorter, such as assigning values to variables based on conditions, and we can use a writing method called "ternary operator":

 age = 20
status = "adult" if age >= 18 else "minor"

This is more compact than writing a full if else , suitable for simple judgment scenarios.

However, this writing method is not suitable for too complex logic and can easily affect readability. It is recommended to use it only when it is clear and clear.


Basically that's it. Mastering if else is the first step in learning Python process control. Although it is not complicated, it is very commonly used in daily programming.

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