Python 2 vs Python 3: Key Differences

Details

What is Python 2?

Python 2 made code development process easier than earlier versions. It implemented technical details of Python Enhancement Proposal (PEP). Python 2.7 (last version in 2.x ) is no longer under development and in 2020 will be discontinued.

In this tutorial, you will learn,

What is Python 3?

On December 2008, Python released version 3.0. This version was mainly released to fix problems which exist in Python 2. The nature of these change is such that Python 3 was incompatible with Python 2. It is backward incompatible Some features of Python 3 have been backported to Python 2.x versions to make the migration process easy in Python 3.

As a result, for any organization who was using Python 2.x version, migrating their project to 3.x needed lots of changes. These changes not only relate to projects and applications but also all the libraries that form part of the Python ecosystem.

KEY DIFFERENCE

  • Python 3 syntax is simpler and easily understandable whereas Python 2 syntax is comparatively difficult to understand.
  • Python 3 default storing of strings is Unicode whereas Python 2 stores need to define Unicode string value with "u."
  • Python 3 value of variables never changes whereas in Python 2 value of the global variable will be changed while using it inside for-loop.
  • Python 3 exceptions should be enclosed in parenthesis while Python 2 exceptions should be enclosed in notations.
  • Python 3 rules of ordering comparisons are simplified whereas Python 2 rules of ordering comparison are complex.
  • Python 3 offers Range() function to perform iterations whereas, In Python 2, the xrange() is used for iterations.

Why should you learn Python 2?

Google Trends Python 2 vs. Python 3

Although, Python 2 is an old open source version here are where you still need to learn Python 2:

Why should you use Python 3?

Stack Overflow Questions Python 2 vs. Python 3

Here, are prime reasons for using Python 3.x versions:

History of Python 2

History of Python 3

Key Differences Between Python 2 and Python 3

Basis of comparison Python 3 Python 2
Release Date

2008 2000
Function print

print ("hello") print "hello"
Division of Integers Whenever two integers are divided, you get a float value When two integers are divided, you always provide integer value.
Unicode

In Python 3, default storing of strings is Unicode. To store Unicode string value, you require to define them with "u".
Syntax

The syntax is simpler and easily understandable. The syntax of Python 2 was comparatively difficult to understand.
Rules of ordering Comparisons In this version, Rules of ordering comparisons have been simplified. Rules of ordering comparison are very complex.
Iteration

The new Range() function introduced to perform iterations. In Python 2, the xrange() is used for iterations.
Exceptions

It should be enclosed in parenthesis. It should be enclosed in notations.
Leak of variables

The value of variables never changes. The value of the global variable will change while using it inside for-loop.
Backward compatibility Not difficult to port python 2 to python 3 but it is never reliable. Python version 3 is not backwardly compatible with Python 2.
Library

Many recent developers are creating libraries which you can only use with Python 3. Many older libraries created for Python 2 is not forward-compatible.

Python 2 vs. Python 3 Example Code

Python 3

def main():
  print("Hello World!")
  
if __name__== "__main__":
  main()

Python 2 

def main():
  print "Hello World!"
  
if __name__== "__main__":
  main()

Which Python Version to Use?

When it comes to Python version 2 vs. 3 today, Python 3 is the outright winner. That's because Python 2 won't be available after 2020. Mass Python 3 adoption is the clear direction of the future.

After considering declining support for Python 2 programming language and added benefits from upgrades to Python 3, it is always advisable for a new developer to select Python version 3. However, if a job demands Python 2 capabilities, that would be an only compelling reason to use this version.

 

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