Python 2 vs. Python 3

What is Python 3

Python 3, released in December 2008, is the most recent version of Python. This version of Python was released to fix the significant problems in the old version, mainly redundancy. It is backward incompatible, meaning that the newer version does not support the code written in the older version. 

Some Python 3 features have been backported to Python 2 versions to simplify the Python 3 migration process.

Also see, Swapcase in Python, And  Convert String to List Python

Differences between Python 2 and Python 3

Print keyword/function

In Python 2, the “print” is treated as a statement. Hence it is not necessary to wrap parenthesis around the text.

# python 2
print 'Hello World!'

You can also try this code with Online Python Compiler

Run Code

In contrast to Python 2, it is treated as a function in Python 3. Hence it is necessary to pass the text you want to print in the function parentheses, or else you will get a syntax error.

# python 3
print('Hello World!')

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Run Code

Taking Input

In Python 2, we would have to use raw_input() to take input from the user.

var = raw_input("Enter the value")

In Python 3, we use input() to take the input from the user. 

var = input("Enter the value")

The main difference between both the functions is that while raw_input() only returns a string, input() instead can return a python type like list, tuple, string, int, etc.

Division Operation

In Python 2, the result of the division operation was always an integer nearest to the actual value.

# python 2
6/5
>> 1

In Python 3, the result of the division operation is always a float value.

# python 3
6/5
>> 1.2

Not equal to operator.

In Python 2, not equals to operator used to be <>

# python 2
var = (1 <> 2)

In Python 3, it was replaced by !=. 

# python 3
var = (1 != 2)

Unicode

In all modern software and information technology protocols, the Unicode encoding standard serves as the foundation for the processing, storing, and interpreting text data in any language. Unicode strings are more versatile than ASCII strings because they can store letters from other languages, as well as emoji and ordinary Roman letters and digits. Python 3 automatically stores Unicode strings, but Python 2 needs you to designate a string with a "u" if you want it to be stored as Unicode. Python 2 stores strings in ASCII form as default.

# python 2 
type('abcd')
>> <type 'str'>
type(b'abcd')
>> <type 'str'>
type(u'abcd')
>> <type 'unicode'>

# python 3 
type('abcd')
>> <type 'str'>
type(b'abcd')
>> <type 'bytes'>
type(u'abcd')
>> <type 'str'>
# in Python 3, str and unicode are same 

Error Handling

There is a minor difference in the syntax between both versions. Instead of comma (‘,’) in Python 2, the ‘as’ keyword is required in Python 3.

# python 2
try :
try_block
except Error_name, err:
print 'Error :', err
# python 3
try :
try_block
except Error_name as err:
print ('Error :', err)

xrange function

The range function returns a list in Python 2, e.g., range(5) will return [0, 1, 2, 3, 4], while the xrange function will return a xrange iterator object. We prefer the range function over the xrange function when iterating over the same range several times since range() returns a static list. The xrange function does not support list techniques such as slicing. The advantage of the xrange function is that it saves memory when the range to iterate is large.

# Python 2
for i in xrange(3):
print(i)
>> 0 
>> 1
>> 2

The xrange function does not exist in Python 3, and the range function of Python 3 is the same as the xrange function of Python 2. 

# Python 3
for i in range(3):
print(i)
>> 0 
>> 1
>> 2

You can also read about the Multilevel Inheritance in Python.

Also see, How to Check Python Version in CMD

Why Are There Different Versions of Python?

Python has different versions because the language has evolved over time to incorporate new features, fix bugs, improve performance, and ensure compatibility with modern technology. Each version is released to address user needs, industry trends, and advances in programming practices.

For example:

• Python 2 was widely used but had limitations, such as a lack of support for modern Unicode standards and inconsistent behavior in certain cases (e.g., integer division).
• Python 3 introduced significant improvements, including better Unicode support, cleaner syntax, and the removal of legacy features that caused confusion or inefficiency.

As technology evolves, updates to Python ensure that the language remains useful, secure, and efficient for developers.

Python 2 or 3: Which Python Version is Best?

Python 3 is the best choice for most developers today because:

1. Active Development: Python 2 reached its end of life in January 2020, meaning it no longer receives updates or security fixes.
2. Modern Features: Python 3 includes better support for Unicode, type hints, async programming, and other modern programming paradigms.
3. Community Support: Most libraries and frameworks now exclusively support Python 3.
4. Future-Proofing: New projects written in Python 3 are more likely to be compatible with future updates.

Frequently Asked Questions

Is Python 2 or 3 better for beginners?

Python 3 is better for beginners due to its cleaner syntax, modern features, and active support, making it easier to learn and use.

Why is Python 2 still used?

Python 2 is still used in legacy systems that haven’t migrated to Python 3 due to compatibility issues or significant redevelopment costs.

Is Python 3 more efficient than Python 2?

Python 3 is generally more efficient, with improved memory management, faster performance in many areas, and better support for modern programming practices.

Conclusion

In this blog, we got introduced to both versions of Python. We also studied where both versions differ and in what aspect they differ. 

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