Python all() Function

The built-in Python function all() checks if all items in a sequence (such as a list, tuple, or set) are True.

It takes one input iterable.

• If all items in iterable evaluate to True, all(iterable) returns True.
• Otherwise, if at least one item evaluates to False, it returns False.
• It iterable is empty, it returns True.

Therefore, all() is the equivalent of:

def all(iterable):
    for i in iterable:
        if not i:
            return False
    return True

It is similar to the function any(), which checks if any of the items are True.

Examples

>>> all([1, 2, 3])
True
>>> all([1, 0, 1])
False
>>> all([])
True
>>> all({1, 2, 2, 3})
True

Input data types

The argument to all() can be any iterable type, including list, tuple, or set.

all() with dict

all() also works with dict. It evaluates the keys, not the values. If at least one key is False, all() returns False.

>>> all({1 : 0, 2 : 1})
True
>>> all({0 : 1, 1 : 2})
False

all() with str

Strings are iterable, so str also works as argument to all(). It returns True even if the string contains spaces or the number zero.

>>> all('Hello')
True
>>> all('Hello world')
True
>>> all('0')
True
>>> all('')
True
>>> all('False')
True

all() does not work with int, float, bool

Data types which are not iterable, such as int and float, do not work as arguments to all(). Even the booleans True, False.

>>> all(1)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'int' object is not iterable

>>> all(1.1)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'float' object is not iterable

>>> all(True)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'bool' object is not iterable

Official documentation

https://docs.python.org/3/library/functions.html#all