Important differences between Python 2.x and Python 3.x with examples

In this article, we will explore some important differences between Python 2.x and Python 3.x with the help of examples, focusing on the following libraries and modules.

• Division operator
• print function
• Unicode
• xrange
• Error Handling
• _future_ module

1. Python Division operator

• In Python 2.x: dividing two integers performs floor division (discards decimals).
• In Python 3.x: dividing two integers performs true division (keeps decimals).

Output in 2.x:

1
-2

Output in 3.x:

1.4
-1.4

2. Print Function in Python

• In Python 2.x: print is a statement (no brackets needed).
• In Python 3.x: print is a function, so parentheses are required.

Output in Python 2.x:
Hello, Geeks
This works too

Output in Python 3.x:
Hello, Geeks

3. Unicode In Python

• Python 2.x: Strings are ASCII by default, unicode must be defined separately.
• Python 3.x: Strings are Unicode by default.

Output in Python 2.x:

<type 'str'>
<type 'str'>

Output in Python 3.x:

<class 'str'>
<class 'bytes'>

 4. xrange() vs range()

Python 2.x:

• range() returns a list.
• xrange() returns a generator (saves memory).

Python 3.x:

• xrange() is removed.
• range() behaves like Python 2’s xrange.

Output in Python 2.x:

1 2 3 4 1 2 3 4

Output in Python 3.x:

NameError: name 'xrange' is not defined

5. Error Handling

• Python 2.x: Uses a comma to bind the exception.
• Python 3.x: Uses as keyword (comma syntax no longer works).

Output in Python 2.x:

name 'not_defined' is not defined Error Caused

Output in Python 3.x:

SyntaxError: invalid syntax

Correct way (works in both):

try:
x = not_defined

except NameError as err:
print(err, 'Error Caused')

6. __future__ module in Python

__future__ module allows Python 2 code to adopt Python 3 features early, making migration easier.

Example 1: Division behavior

Output (Python 2.x with future import):

1.4 
-1.4

Output (Python 3.x):

1.4
-1.4

Example 2: print as a function

Output (Python 2.x with future import):

GeeksforGeeks

Output (Python 3.x with future import):

GeeksforGeeks

Related Articles:

• Python Keywords and Identifiers
• Python Operators