Python all() method

There are innumerable built-in methods in Python which fulfill a wide variety of purposes in the world of technology. Today, we will explore the all method in Python.

Python all() method

The all() method is a built-in Python method that checks whether the values inside an iterable are true or false.

Syntax of this method:

all(iterable)

It returns true if all the values present inside an iterable (like list, tuple, dictionary) are true and returns false otherwise. It takes a single parameter which could be a list or tuple or dictionary or any other iterable that contains data elements.

Below are the rules which the all method uses while evaluating an iterable:

1. If all values are true, return True.

2. If all values are false, return False.

3. If an empty iterable is passed as a parameter, return True.

4. If only one of the values inside the iterable is true and all other values are false, return False.

5. If only one of the values inside the iterable is false and all other values are true, return False.

Now let us look at how the all method works with strings, lists, and dictionaries with the help of separate examples.

1. all() with strings

my_str = "Hi, this is StudyTonight"
print(all(my_str))

my_str = '000'  # 0 is a False value, but 0 inside quotes is a string, hence a true value
print(all(my_str))

my_str = ''   # all with empty string
print(all(my_str))

Output:

True
True
True

2. all() with list object

As mentioned earlier, an empty list passed as a parameter to all method returns True. Understand the rules which the all method follows to determine the output of all method when it is used with different values in a list data structure.

my_list = [1, 3, 2, 5, 1.23, 5.67]
print(all(my_list))

my_list = [False, 0]  # A list that contains values which is equivalent to False
print(all(my_list))

my_list = [False, 0, 5.0]  # When one value is True and other values are False
print(all(my_list))

my_list = [1, 1.23, 5.67, 0]  # When one value is False, and all other values are True. 0 is false
print(all(my_list))

my_list = []   # When an empty list(iterable) is passed
print(all(my_list))

Output:

True
False
False
False
True

3. all() with dictionary object

Execute the below lines of code separately to understand the output.

my_dict = {0: 'False', 1: 'False'}
print(all(my_dict))

my_dict = {1: 'True', 2: 'True'}
print(all(my_dict))

my_dict = {1: 'True', False: 0}
print(all(my_dict))

my_dict = {1: 'True', False: '0'}
print(all(my_dict))

my_dict = {}    # Empty dictionary passed as parameter to all
print(all(my_dict))

# 0 (integer) is considered to be a False value, whereas '0' (string 0) 
# is considered to be a True value
my_dict = {'0': 'True'}

print(all(my_dict))

Output:

False
True
False
False
True
True

Conclusion:

In this post, we understood how the all() method works with different data structures and types. To execute and see the code examples running, try executing the above code on our Python Playground available on our website.