Key Differences Between Python 2 and Python 3

Python, created in the early 1990s, has grown into a mature language whose popularity surged with the rise of big data. Python 2, first released in 2001 and stabilized around 2006‑2008, dominated early development, while Python 3 debuted in 2008 but only became stable around 2014.

Officially, Python 2 reached end‑of‑life in 2020, and Python 3.x (often called Python 3000 or Py3k) introduced many non‑backward‑compatible changes, prompting developers to migrate.

Encoding differences : Python 2 defaults to ASCII, causing frequent Unicode errors when handling Chinese or other non‑ASCII characters. Python 3 defaults to UTF‑8, providing native Unicode strings and a separate bytes type, simplifying string handling.

Example of encoding handling in Python 3:

# source file is UTF‑8 by default
s = "中文变量"
print(s)

Exception syntax : Python 2 uses except Exception, e:, while Python 3 requires except Exception as e:. Moreover, only objects derived from BaseException can be raised in Python 3.

Exception handling example:

# Python 2
try:
    raise Exception, "error"
except Exception, e:
    print(e)
    return False

# Python 3
try:
    raise Exception("error")
except Exception as e:
    print(e)
    return False

Range functions : Python 2 provides xrange() for lazy iteration and a faster range() that returns a list. Python 3 removes xrange and makes range() behave like xrange, returning a lazy sequence.

Print statement : In Python 2, print is a statement (e.g., print "text") and also works as a function in later 2.x versions. Python 3 makes print a function, requiring parentheses.

Input handling : Python 2 distinguishes input() (evaluates the input) and raw_input() (returns a string). Python 3 removes raw_input; input() always returns a string.

Conclusion: The core programming concepts are consistent across versions, so once you master Python, switching between 2 and 3 is quick. Choose Python 2 only if legacy third‑party libraries or enterprise environments require it; otherwise, adopt Python 3 for future‑proof development.