What does a double equal sign mean in Python?

What does == mean in Python?

Short answer: == is the equality operator. It compares two values and returns True if they are equal and False if they are not: 5 == 5.0 is True and "5" == 5 is False. Do not confuse it with =, which assigns a value to a variable, or with is, which checks whether two names point to the same object.

You use == mostly inside conditions, such as if answer == "yes":, but it is an expression like any other: result = (a == b) stores True or False in result.

= stores a value, == compares values and is compares identity. Two lists with the same items are equal, but they are not the same object.

= vs == vs is at a glance

How == compares different types

Python compares the values, and some types count as equal to each other:

print(5 == 5.0)        # True, int and float with the same value
print(True == 1)       # True, bool is a kind of int
print("5" == 5)        # False, a string is never equal to a number
print("a" == "A")      # False, comparisons are case-sensitive
print([1, 2] == [1, 2])  # True, same items in the same order
print([1, 2] == [2, 1])  # False, order matters in lists
print({"a": 1, "b": 2} == {"b": 2, "a": 1})  # True, order does not matter in dicts
print((1, 2) == [1, 2])  # False, a tuple is not a list

Data that comes from input(), a file or an API is usually text, so convert it before comparing with numbers: int(answer) == 5.

== vs is

is checks identity: whether both names point to the exact same object. Two lists can be equal without being the same list:

a = [1, 2]
b = [1, 2]
c = a
 
print(a == b)  # True, same content
print(a is b)  # False, two different lists
print(a is c)  # True, c is another name for a

Use is only to compare with None, True or False as singletons, as in if result is None:. For numbers and strings, always use ==. If you write x is 1, Python warns you: SyntaxWarning: "is" with 'int' literal. Did you mean "=="?.

== vs = in a condition

A single = inside an if is a syntax error in Python, and the message points you to the fix:

if x = 5:
    ...
# SyntaxError: invalid syntax. Maybe you meant '==' or ':=' instead of '='?

:=, the walrus operator, assigns a value inside an expression. It is useful in loops and conditions, but it is never a comparison.

Compare floats with math.isclose()

Floats are stored in binary, so some decimal results have tiny errors:

import math
 
print(0.1 + 0.2)                     # 0.30000000000000004
print(0.1 + 0.2 == 0.3)              # False
print(math.isclose(0.1 + 0.2, 0.3))  # True

Use math.isclose() to compare floats, or the decimal module when you need exact decimal arithmetic, such as with money. A special case: float("nan") == float("nan") is False; check it with math.isnan().

Use == with AI

An AI assistant such as ChatGPT, Claude or GitHub Copilot can explain a comparison that does not behave as you expect. Give it the two values, their types and the result you got. These three prompts are ready to copy.

1. Explain a comparison that returns False

In Python, this comparison returns [False] but I expected [True]:
[paste the line, e.g. if answer == 5:]
The values are: [paste them, and the output of print(type(answer))]
Explain why and give me the fix.

2. Choose between ==, is and isclose()

In my Python code I compare [prices / user names / API responses / None values].
Tell me whether I should use ==, is or math.isclose() in each case and why.
This is my code: [paste it]

3. Make my class comparable

I have this Python class: [paste it]
Two objects with the same data return False with ==.
Show me how to add __eq__, or how to turn it into a dataclass, and write tests for it.

Check the answer by printing both values and their types with print(repr(a), type(a)).

Compare strings without case or extra spaces

== compares strings character by character, so "Yes", "yes" and "yes " are three different values. Normalize them first:

answer = " Yes "
print(answer == "yes")                  # False
print(answer.strip().lower() == "yes")  # True

For text in other languages, casefold() is more complete than lower(): "Straße".casefold() == "STRASSE".casefold() is True.

Compare several values at once

Python lets you chain comparisons, and in replaces several == joined with or:

a = b = c = 7
print(a == b == c)  # True, the same as a == b and b == c
 
color = "red"
print(color == "red" or color == "blue")  # True
print(color in ("red", "blue"))           # True, shorter

== with your own classes

By default, two objects of your own class are only equal if they are the same object. A dataclass compares the fields for you:

from dataclasses import dataclass
 
@dataclass
class Point:
    x: int
    y: int
 
print(Point(1, 2) == Point(1, 2))  # True

Without @dataclass, the same comparison returns False unless you write an __eq__ method.

Common errors with == in Python

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