Python all() Function

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

all() Syntax

all(iterable)

all() Parameters

Python all() function parameters:

all() Return Value

Python all() function returns:

• True: if all elements in an iterable are true
• False: if any element in an iterable is false

Falsy Values in Python

Falsy values are those that evaluate to False in a boolean context:

• Constants defined to be false: None and False.
• Zero of any numeric type: Integer (0), Float (0.0), Complex (0j), Decimal(0), Fraction(0, 1).
• Empty sequences and collections: Lists ([]), Tuples (()), Dictionaries ({}), Sets (set()), Strings (""), range(0)
• Any custom object for which the __bool__() method is defined to return False, or the __len__() method returns 0 when __bool__() is not defined.

Examples

Some examples of how to use all() function.

all() function on List

my_list = [1, 1, 1]
print(all(my_list))   # Output: True

my_list = [0, 1, 1]
print(all(my_list))   # Output: False

output

True
False

Other examples:

my_list = [True, 0, 1]
print(all(my_list))   # Output: False

my_listT = ('', 'red', 'green')
print(all(my_list))   # Output: False

my_list = {0j, 3+4j}
print(all(my_list))   # Output: False

output

False
False
False

all() function on String

s = "This is good"
print(all(s))   # Output: True

s = '000'
print(all(s))   # Output: True

s = ''
print(all(s))   # Output: True

output

True
True
True

all() function on Dictionary

The function all() can be used on dictionaries.

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

dict1 = {0: 'Zero', 1: 'One', 2: 'Two', 3: 'Three'}
print(all(dict1))   # Output: False

dict2 = {'Zero': 0, 'One': 1, 'Two': 2, 'Three': 3}
print(all(dict2))   # Output: True

output

False
True

all() function on Empty Iterable

The function all() can be used on iterables. In particular, if the iterable is empty, the function returns True.

my_list = []
print(all(my_list))   # Output: True

my_list = [[], []]
print(all(my_list))   # Output: False

output

True
False