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Common Python Mistakes and How to Fix Them

bookComparison and Boolean Logic Mistakes

Understanding how Python distinguishes between assignment and comparison is essential for writing correct code. The assignment operator (=) is used to give a value to a variable, while the comparison operator (==) checks whether two values are equal. Mixing these up is a frequent source of bugs, especially in conditional statements. If you use = instead of == in a condition, Python will raise a syntax error because assignment is not allowed inside expressions that expect a boolean value, such as if statements.


              
1234

            
# This code will cause a syntax error:
x = 5
if x = 10:
    print("x is ten")
copy

Boolean Logic Operators and Common Mistakes

Python uses boolean logic operators—and, or, and not—to combine or modify conditions in your code. These operators are essential for creating complex logical tests:

  • and: Both conditions must be true for the whole expression to be true;
  • or: At least one condition must be true for the expression to be true;
  • not: Inverts the truth value of a condition.

Common mistakes include:

  • Using = (assignment) instead of == (comparison) in a condition, as shown in the earlier code sample. This leads to a syntax error because assignment is not valid inside an if statement;
  • Confusing and with or, which can cause your logic to behave differently than you expect;
  • Misunderstanding how not affects the result of an expression.

Always check that you use the correct operator for your intended logic. For example, a == 10 and b == 10 only returns True if both a and b are exactly 10, while a == 10 or b == 10 returns True if either one is 10. Double-check your conditions to avoid subtle bugs.

1. Which operator should you use to check if two values are equal in a Python condition?

2. Fill in the blanks so that the function returns True only if both a and b are equal to 10.

question mark

Which operator should you use to check if two values are equal in a Python condition?

Select the correct answer

question-icon

Fill in the blanks so that the function returns True only if both a and b are equal to 10.

def both_ten(a, b): return a 10 and b 10 print(both_ten(10, 10)) print(both_ten(10, 5))
True
False

Click or drag`n`drop items and fill in the blanks

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bookComparison and Boolean Logic Mistakes

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Understanding how Python distinguishes between assignment and comparison is essential for writing correct code. The assignment operator (=) is used to give a value to a variable, while the comparison operator (==) checks whether two values are equal. Mixing these up is a frequent source of bugs, especially in conditional statements. If you use = instead of == in a condition, Python will raise a syntax error because assignment is not allowed inside expressions that expect a boolean value, such as if statements.


              
1234

            
# This code will cause a syntax error:
x = 5
if x = 10:
    print("x is ten")
copy

Boolean Logic Operators and Common Mistakes

Python uses boolean logic operators—and, or, and not—to combine or modify conditions in your code. These operators are essential for creating complex logical tests:

  • and: Both conditions must be true for the whole expression to be true;
  • or: At least one condition must be true for the expression to be true;
  • not: Inverts the truth value of a condition.

Common mistakes include:

  • Using = (assignment) instead of == (comparison) in a condition, as shown in the earlier code sample. This leads to a syntax error because assignment is not valid inside an if statement;
  • Confusing and with or, which can cause your logic to behave differently than you expect;
  • Misunderstanding how not affects the result of an expression.

Always check that you use the correct operator for your intended logic. For example, a == 10 and b == 10 only returns True if both a and b are exactly 10, while a == 10 or b == 10 returns True if either one is 10. Double-check your conditions to avoid subtle bugs.

1. Which operator should you use to check if two values are equal in a Python condition?

2. Fill in the blanks so that the function returns True only if both a and b are equal to 10.

question mark

Which operator should you use to check if two values are equal in a Python condition?

Select the correct answer

question-icon

Fill in the blanks so that the function returns True only if both a and b are equal to 10.

def both_ten(a, b): return a 10 and b 10 print(both_ten(10, 10)) print(both_ten(10, 5))
True
False

Click or drag`n`drop items and fill in the blanks

Alt var klart?

Hvordan kan vi forbedre det?

Takk for tilbakemeldingene dine!

Seksjon 3. Kapittel 1
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