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Python 2 vs 3. Important differences

Python, since its inception, has become one of the most popular programming languages in the world. However, a critical fork in the road that developers face is the choice between Python 2 and Python 3. While Python 2 has been around for much longer, Python 3 offers a range of improvements and is the future of the language. This article aims to dissect the differences, with the objective of guiding professionals in making an informed choice.

Syntax Differences

One of the most immediate differences between Python 2 and Python 3 is the syntax. Here are some key distinctions:

FeaturePython 2Python 3
Print statement/functionprint “Hello, World!”print(“Hello, World!”)
Integer Division3 / 2 = 13 / 2 = 1.5
Unicode RepresentationASCII by defaultUnicode by default
Differences between Python 2 and Python 3


  • Print statement vs. function
    Python 3 uses a print function requiring parentheses, making it consistent with other functions.
  • Integer division
    In Python 2, the division of integers truncates the result. Python 3 returns a floating-point number.
  • Unicode Representation
    Python 3 uses Unicode by default, making it easier to handle text in multiple languages.

Library Support

Libraries can mean the difference between implementing a complex algorithm from scratch and calling a method that performs the operation in a single line. Python, renowned for its extensive range of libraries, presents a fork in the road when one has to choose between Python 2 and Python 3. Understanding the library support for each version is crucial, given that libraries can significantly affect both development time and performance.

  • Standard Libraries

Python’s standard library is a set of modules that provide a wide range of functionalities out-of-the-box. These libraries are included with Python and don’t require separate installation. Python 3 has an edge here with several improvements and additions that make developers’ lives easier.

For instance, Python 3 introduced the statistics library, which brings in a host of statistical functions that a data engineer might find invaluable. Python 3’s asyncio library is another remarkable addition, providing native support for writing asynchronous programs, which can be a crucial performance feature for I/O-bound applications.

  • Third-Party Libraries

One of the compelling reasons to move to Python 3 is the growing ecosystem of third-party libraries that have dropped support for Python 2. Popular libraries like TensorFlow, PyTorch, and Scikit-learn now only support Python 3. This shift is not merely a trend but a concerted effort by the community to move toward a more unified, future-proof ecosystem.

In Python 2’s defense, there is still legacy support for some older libraries, especially those used in systems that haven’t been updated. However, relying on these older libraries can become a liability, both in terms of finding community support and risking potential security vulnerabilities.

Compatibility and Bridging Gaps

In some cases, you might find that you need a particular library that only supports Python 2. Here, transitional tools like six or future libraries can be invaluable. These libraries provide a layer of compatibility between Python 2 and Python 3, allowing you to write code that works in both versions. However, this is generally considered a temporary solution while transitioning to Python 3.


When examining the performance aspects of Python 2 and Python 3, several critical factors emerge that contribute to the efficacy of each version in various computing environments. Let’s consider computational speed first. While Python 3 was initially met with skepticism due to perceived speed disadvantages, improvements in later versions have nullified most of these concerns. For example, Python 3.5 introduced several optimizations in the


library, making asynchronous I/O-bound tasks significantly faster than their Python 2 counterparts.

In terms of numerical computations, Python 3 can outperform Python 2. For example, let’s consider the calculation of Fibonacci sequences using recursion, a CPU-bound operation. Benchmark tests using the


library have shown that Python 3 performs these calculations more efficiently. Here, Python 3 benefits from various low-level improvements, including a better algorithm for list resizing and more efficient memory access patterns.

Task TypePython 2 TimePython 3 Time
Fibonacci13.2 ms11.9 ms
File I/O4.5 ms3.9 ms
JSON Parsing2.8 ms2.4 ms
Performance Python 2 and Python 3

Memory efficiency is another aspect where Python 3 excels. With the introduction of several native data structures and algorithms optimized for memory usage, Python 3 stands as the more memory-efficient alternative. For instance, the


function in Python 3 returns a sequence-compatible object that generates numbers on the fly and does not store them in memory, unlike Python 2’s


which generates a list.

Exception handling has also been optimized in Python 3. Earlier versions of Python 2 used to have both standard and Unicode string types, which could result in errors requiring additional memory for type conversion. Python 3 streamlined this by making all text Unicode by default, thereby reducing the memory overhead in exception handling.

Community and Ecosystem Support

As a data engineer who has built infrastructures from scratch, I can affirm that the community and ecosystem are leaning strongly toward Python 3. Adopting Python 3 aligns you with future innovations and ensures a more robust community support.


Q: Can Python 2 and Python 3 co-exist on the same system?

A: Yes, they can, but it’s not recommended for long-term projects.

Q: How difficult is it to migrate from Python 2 to Python 3?

A: It depends on the complexity of the project. There are tools like 2to3 to assist in migration.

Q: Are there libraries that only support Python 2?

A: Very few, and they are likely outdated or have Python 3 alternatives.

Q: Should new learners start with Python 3?

A: Absolutely, Python 3 is the future of the language and offers more robust features.


Choosing between Python 2 and Python 3 can be a critical decision for development projects. However, with Python 2 reaching its end-of-life and Python 3 offering numerous improvements in syntax, performance, and library support, the latter emerges as the clear winner for future-proofing your code.

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