Best Practices for Conditional Statements in Python

This article explains the best practices for conditional statements in Python.

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Best Practices for Conditional Statements in Python

The if statement in Python is a fundamental construct for implementing conditional branching, and it greatly impacts code readability and maintainability. Here, we will discuss in detail the best practices for using if statements.

Use explicit conditional expressions

Write conditional expressions concisely and explicitly, avoiding redundant statements.

1condition = True
2
3### Bad Example
4if condition == True:
5    pass
6
7### Good Example
8if condition:
9    pass

• In Python, you can indicate that a condition is true by writing if condition:.

Combining multiple conditions

When combining multiple conditions, use and or or. However, when conditional expressions become complex, readability may decrease, so consider the following adjustments:.

 1age = 15
 2is_student = True
 3
 4### Bad Example
 5# Complex condition
 6if (age > 18 and age < 65) or (is_student and age > 15):
 7    pass
 8
 9### Good Example
10# Improving readability
11is_working_age = 18 < age < 65
12is_eligible_student = is_student and age > 15
13
14if is_working_age or is_eligible_student:
15    pass

• By splitting conditions and assigning them to variables, readability can be improved.

and/or short-circuit evaluation

In conditional expressions using and or or, if the result can be determined by only the left-hand value, short-circuit evaluation occurs and the right-hand side is not evaluated. Understanding this helps you avoid unnecessary processing and prevent errors.

 1user = None
 2def expensive_check():
 3    return True
 4
 5# Example of short-circuiting with 'and'
 6if user and user.is_active:
 7    # If user is None, user.is_active will NOT be evaluated
 8    print("Active user found.")
 9
10# Example of short-circuiting with 'or'
11if user.is_admin or expensive_check(user):
12    # If user.is_admin is True, expensive_check will NOT be called.
13    print("Access granted.")
14else:
15    print("Access denied.")

• By utilizing short-circuit evaluation, you can improve processing efficiency and safety.

Precedence of and and or

and has higher precedence than or. Therefore, when combining conditions naively, you may get unintended results. It's important to use parentheses to make your intentions clear.

 1age = 15
 2is_student = True
 3
 4### Unclear example
 5# This is interpreted as: age > 18 and (age < 65 or is_student)
 6if age > 18 and age < 65 or is_student:
 7    pass
 8
 9### Clear example
10# Explicit parentheses make the intended logic obvious
11if (age > 18 and age < 65) or is_student:
12    pass

• By using parentheses, you can clarify the precedence of and and or, reducing the risk of unexpected bugs.

Understand Truthy and Falsy

In Python, the following values are evaluated as False:.

• None
• False
• The number 0 (including 0.0)
• Empty sequence types (such as empty lists, tuples, or strings)
  • Examples: [], (), ""
• Empty dictionary
  • Example: {}

Leveraging this can help simplify your conditional expressions.

1items = [1, 2, 3]
2
3### Bad Example
4if len(items) > 0:
5    pass
6
7### Good Example
8if items:
9    pass

Proper use of elif and else

When evaluating multiple conditions, use elif. Use else to define a default behavior at the end.

 1score = 80
 2
 3if score >= 90:
 4    grade = "A"
 5elif score >= 80:
 6    grade = "B"
 7elif score >= 70:
 8    grade = "C"
 9else:
10    grade = "F"

• else is not mandatory. If all conditions are covered, it can be omitted.
• Pay attention to the order of conditional expressions and arrange them logically without redundancy.

Limit the depth of nesting.

Deep nesting of if statements makes the code harder to read.

 1def access_resource():
 2    return True
 3
 4### Bad Example
 5def deep_nest(user, resource):
 6    if user.is_authenticated:
 7        if user.has_permission:
 8            if resource.is_available:
 9                access_resource()
10
11### Good Example
12def early_return(user, resource):
13    if not user.is_authenticated:
14        return
15    if not user.has_permission:
16        return
17    if not resource.is_available:
18        return
19
20    access_resource()

• Using early returns can reduce nesting and make the code more concise.

Avoid using single-line if statements

It is possible to write if statements in a single line, but this may reduce readability.

 1condition = False
 2def do_something():
 3    return True
 4
 5### Bad Example
 6if condition: do_something()
 7
 8### Good Example
 9if condition:
10    do_something()

• Using single-line if statements is acceptable only for short conditions or actions, but avoid writing overly verbose code.

Simplifying with the ternary operator or or

For simple conditional branches, using the ternary operator or or can make your code more concise. However, overusing these can make your code harder to read, so they should only be used for simple and intuitive conditions.

 1is_admin = True
 2input_name = None
 3
 4# Regular if statement
 5if is_admin:
 6    role = "Administrator"
 7else:
 8    role = "User"
 9
10# Simplified using an inline if
11role = "Administrator" if is_admin else "User"
12
13# Use 'or' to provide a default value
14name = input_name or "Guest"

• For simple conditions, using the ternary operator or or can make your code shorter and easier to understand.

Caching conditional expressions.

Conditional expressions involving expensive calculations or function calls can be cached in variables to improve performance.

 1def expensive_function():
 2    pass
 3
 4def another_expensive_function():
 5    pass
 6
 7### Bad Example
 8if expensive_function() and another_expensive_function():
 9    pass
10
11### Good Example
12result1 = expensive_function()
13result2 = another_expensive_function()
14if result1 and result2:
15    pass

Summary

Python's if statements are simple and powerful tools, but improper use can make code complex and hard to read. By adopting the best practices introduced here, you can improve the readability, maintainability, and efficiency of your code.

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