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Python Built-in Methods – Python all() Function

By on Thursday, May 13, 2021

Python all() Function

Determines whether all items in an iterable are True

Usage

The all() function returns True if all items in an iterable are True. Otherwise, it returns False.

If the iterable is empty, the function returns True.

Syntax

all(iterable)

Parameter Condition Description
iterable Required An iterable of type (list, string, tuple, set, dictionary etc.)

Falsy Values

In Python, all the following values are considered False.

  • Constants defined to be false: None and False.
  • Zero of any numeric type: 0, 0.0, 0j, Decimal(0), Fraction(0, 1)
  • Empty sequences and collections: '', (), [], {}, set(), range(0)

Basic Examples

# Check if all items in a list are True

L = [1, 1, 1]
print(all(L))   # Prints True

L = [0, 1, 1]
print(all(L))   # Prints False

Here are some scenarios where all() returns False.

L = [True, 0, 1]
print(all(L))   # Prints False

T = ('', 'red', 'green')
print(all(T))   # Prints False

S = {0j, 3+4j}
print(all(S))   # Prints False

all() on a Dictionary

When you use all() function on a dictionary, it checks if all the keys are true, not the values.

D1 = {0: 'Zero', 1: 'One', 2: 'Two'}
print(all(D1))   # Prints False

D2 = {'Zero': 0, 'One': 1, 'Two': 2}
print(all(D2))   # Prints True

all() on Empty Iterable

If the iterable is empty, the function returns True.

# empty iterable
L = []
print(all(L))   # Prints True

# iterable with empty items
L = [[], []]
print(all(L))   # Prints False

 

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