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Datatyper i Python

bookLogiske operatorer

People say yes and yes, yes or no, definitely not. In Python, the logical operators and, or, and not express these ideas formally and produce Booleans (True/False) you'll use with comparisons in if/while.

What Each Operator Means

Precedence

not binds tighter than and, which binds tighter than or (not > and > or). Use parentheses when in doubt.

For instance, age >= 18 and has_id is True only if both checks succeed:


              
123

            
age = 21
has_id = True
print(age >= 18 and has_id)   # True
copy

Truth Table

A truth table lists all possible truth values of inputs and shows the resulting output of a logical expression. It's a compact way to reason about logic without running code.

Using the Table

If X is False and Y is True, then X and Y is False, X or Y is True, and not X is True.

Return Values & Short-Circuiting (Together)

and and or don't always yield the words True/False, they return one of their operands, and Python may stop early once the result is known.

  • A and B:

    • If A is falsey, the whole expression is false and the result is A (Python does not evaluate B);
    • If A is truthy, the result depends on B and the expression evaluates to B.

  • A or B:

    • If A is truthy, the expression is true and the result is A (Python does not evaluate B);
    • If A is falsey, the result depends on B and the expression evaluates to B.

  • not X always returns an actual Boolean: True or False.


              
1234567891011121314151617

            
# Choosing a display name for a user profile
username = ""             # user didn't set a custom name
print(username or "Guest")   # "Guest" → fallback to default name

username = "Alice"
print(username or "Guest")   # "Alice" → custom name is used

# Checking login attempts and access permissions
login_attempts = 0
access_level = 123
print(login_attempts and access_level)  # 0 → login not yet attempted

login_attempts = 5
print(login_attempts and access_level)  # 123 → user has access after attempts

# Checking empty and non-empty values
print(not 0, not "Hello")  # True False → 0 is falsey, non-empty string is truthy
copy

1. Fill the blanks with True or False). Let X = True, Y = False.

2. Which statement matches classical logic for "neither X nor Y"?

3. What does the expression return?

question-icon

Fill the blanks with True or False). Let X = True, Y = False.

X and Y →
not X →
X or Y →
question mark

Which statement matches classical logic for "neither X nor Y"?

Select the correct answer

question mark

What does the expression return?

Select the correct answer

Alt var klart?

Hvordan kan vi forbedre det?

Takk for tilbakemeldingene dine!

Seksjon 2. Kapittel 4

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bookLogiske operatorer

Sveip for å vise menyen

People say yes and yes, yes or no, definitely not. In Python, the logical operators and, or, and not express these ideas formally and produce Booleans (True/False) you'll use with comparisons in if/while.

What Each Operator Means

Precedence

not binds tighter than and, which binds tighter than or (not > and > or). Use parentheses when in doubt.

For instance, age >= 18 and has_id is True only if both checks succeed:


              
123

            
age = 21
has_id = True
print(age >= 18 and has_id)   # True
copy

Truth Table

A truth table lists all possible truth values of inputs and shows the resulting output of a logical expression. It's a compact way to reason about logic without running code.

Using the Table

If X is False and Y is True, then X and Y is False, X or Y is True, and not X is True.

Return Values & Short-Circuiting (Together)

and and or don't always yield the words True/False, they return one of their operands, and Python may stop early once the result is known.

  • A and B:

    • If A is falsey, the whole expression is false and the result is A (Python does not evaluate B);
    • If A is truthy, the result depends on B and the expression evaluates to B.

  • A or B:

    • If A is truthy, the expression is true and the result is A (Python does not evaluate B);
    • If A is falsey, the result depends on B and the expression evaluates to B.

  • not X always returns an actual Boolean: True or False.


              
1234567891011121314151617

            
# Choosing a display name for a user profile
username = ""             # user didn't set a custom name
print(username or "Guest")   # "Guest" → fallback to default name

username = "Alice"
print(username or "Guest")   # "Alice" → custom name is used

# Checking login attempts and access permissions
login_attempts = 0
access_level = 123
print(login_attempts and access_level)  # 0 → login not yet attempted

login_attempts = 5
print(login_attempts and access_level)  # 123 → user has access after attempts

# Checking empty and non-empty values
print(not 0, not "Hello")  # True False → 0 is falsey, non-empty string is truthy
copy

1. Fill the blanks with True or False). Let X = True, Y = False.

2. Which statement matches classical logic for "neither X nor Y"?

3. What does the expression return?

question-icon

Fill the blanks with True or False). Let X = True, Y = False.

X and Y →
not X →
X or Y →
question mark

Which statement matches classical logic for "neither X nor Y"?

Select the correct answer

question mark

What does the expression return?

Select the correct answer

Alt var klart?

Hvordan kan vi forbedre det?

Takk for tilbakemeldingene dine!

Seksjon 2. Kapittel 4
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