Python's one line if else is a ternary operator, written as x if condition else y, which is used to simplify simple conditional judgment. It can be used for variable assignment, such as status = "adult" if age >= 18 else "minor"; it can also be used to directly return results in functions, such as def get_status(age): return "adult" if age >= 18 else "minor"; although nested use is supported, such as result = "A" if score > 90 else "B" if score > 70 else "C", it is recommended not to exceed one layer to maintain readability; when using it, you should keep the logic simple, avoid side effects, and pay attention to format alignment to improve code clarity.
When writing Python code, sometimes I want to express a simple if else judgment with one line. In fact, Python provides a concise one-line writing method, which can make you easier when assigning values or returning results.

What is Python's one line if else
The ternary operator in Python is the so-called "one line if else". Its basic writing is:
x if condition else y
The meaning of this structure is: if condition is true, take the value of x; otherwise, take the value of y. It is very suitable for simplifying some simple judgment logic, such as variable assignment, function return value and other scenarios.

Common ways to use and suggestions
Used for variable assignment
This is one of the most common uses, for example, you want to determine the value of a variable based on a certain condition:
status = "adult" if age >= 18 else "minor"
This method is more compact than writing a complete if-else, suitable for scenarios with clear logic and uncomplicated branching content.

Return directly in the function
If your function only needs to return different values according to the conditions, you can also use this writing method to make the function body more concise:
def get_status(age): return "adult" if age >= 18 else "minor"
This way, it looks clean and neat and easy to read.
Nesting with caution
Although it can be used in nesting, it is recommended not to exceed one layer. For example:
result = "A" if score > 90 else "B" if score > 70 else "C"
Although the syntax is fine, it is a bit confusing to read. Too much nesting will reduce readability, so it is better to use regular if-else at this time.
Things to note in practical applications
Keep the logic simple : one line if else is most suitable for single judgment and quick return. It is better to disassemble the complex logic and write it clearly.
Format alignment helps read : even if one line is finished, appropriate spaces or newlines can improve readability, such as:
status = "adult" \ if age >= 18 \ else "minor"
Avoid side effects : Do not perform side effects operations in ternary expressions, such as modifying states, calling functions, etc., which will make the code difficult to understand.
In general, Python's one line if else is a practical trick, and using it well can make the code more concise. But be careful not to abuse it, especially when the logic is complex or nested with multiple layers, it is more important to keep it clear.
Basically that's it.
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