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How to Compare Multiple Variables in Python

This guide explores various efficient and Pythonic methods for comparing multiple variables in Python. We'll cover:

  • Checking if multiple variables have the same value.
  • Checking if multiple variables are equal to a specific value.
  • Checking if a variable is not equal to multiple values.
  • Checking if a variable is equal to any of several values.
  • Using the all() and any() functions for cleaner comparisons.

Checking if All Variables Have the Same Value​

Using multiple equality comparisons (==)​

The simplest way to check if all variables have the same value is to chain equality comparisons:

a = 123
b = 123
c = 123

if a == b == c:
    print('Multiple variables are equal')
else:
    print('Multiple variables are not equal')

Output:

Multiple variables are equal
  • This approach is readable and efficient for a small number of variables.

Checking equality within a sequence (list/tuple)​

If your variables are already in a list or tuple (or you can easily put them in one), you can use the count() method and check the length, or use the all() function:

a = 123
b = 123
c = 123

my_list = [a, b, c]

#Method 1: count()
if my_list.count(my_list[0]) == len(my_list):
    print('Multiple variables are equal')  # Output: Multiple variables are equal
else:
    print('Multiple variables are not equal')

#Method 2: all()
if all(item == my_list[0] for item in my_list):
    print('Multiple variables are equal') # Output: Multiple variables are equal

  • count() returns the number of occurrences of a value in a list.
  • all() is used with a generator expression that checks if all the elements of the list are equal to the first element of the list.
  • Both methods are very efficient for checking equality within a sequence.

Checking if All Variables Equal a Specific Value​

To check if all variables are equal to a specific value, you can again use chained equality or all():

a = 123
b = 123
c = 123

# Chained equality
if a == b == c == 123:
    print('Variables are equal to the value')  # Output: Variables are equal to the value

# Using all() with a list/tuple
variables = [a, b, c]
if all(v == 123 for v in variables):
    print('Variables are equal to the value') # Output: Variables are equal to the value

Checking if a Variable is NOT Equal to Multiple Values​

Using not in​

The most readable and Pythonic way to check if a variable is not equal to any of several values is to use the not in operator:

my_str = 'another'
multiple_values = ['tutorial', 'reference', 'com']

if my_str not in multiple_values:
    print('The variable is NOT equal to any of the specified values')
else:
    print('The variable is equal to one of the specified values')

print(my_str not in multiple_values)  # Output: True

Output:

The variable is NOT equal to any of the specified values
True
  • The not in method is much more readable than multiple chained != conditions.

Using all()​

You can also use all() with a generator expression, which is functionally equivalent to not in but might be preferred in some contexts for consistency:

my_str = 'another'
multiple_values = ['tutorial', 'reference', 'com']

if all(my_str != item for item in multiple_values):
    print('The variable is NOT equal to any of the specified values')
else:
    print('The variable is equal to one or more of the specified values')

Output:

The variable is NOT equal to any of the specified values

Checking if a Variable Equals ANY of Several Values​

To check if a variable is equal to any of several values, use the in operator:

my_str = 'tutorial'
two_values = ('tutorial', 'reference')  # Tuple is slightly more efficient than a list

if my_str in two_values:
    print('The variable is equal to one of the two values') # Output: The variable is equal...
else:
    print('The variable is NOT equal to any of the specified values')
  • my_str in two_values checks if the string is equal to any of the values, and returns True if it is.

Using any()​

For completeness, here's the any() approach, which is equivalent but less readable than in:

my_str = 'tutorial'
two_values = ('tutorial', 'reference')

if any(my_str == item for item in two_values):
    print('The variable is equal to one of the two values') # Output: The variable is equal...
else:
    print('The variable is NOT equal to any of the specified values')

Conclusion​

This guide presented different ways to compare variables and values in Python.

You learned how to:

  • compare the same value to a list, using all() or the in operator.
  • Use chained equality checks (a == b == c) when you need to verify that all variables hold the same value.
  • Use in and not in for concise membership testing. For checking multiple variables against a single value or another set of variables, all() with a generator expression is generally the most efficient and readable approach.

Choose the technique that best reflects the logic of your comparison and enhances code clarity.

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