What is future in Python used for and how/when to use it, and how it works

Deciding when to use future

Wondering when to use __future__? Here's how to decide:

• If you want to future-proof your code against changes in upcoming Python versions.
• If you're preparing to upgrade to a newer version of Python and need your code to remain compatible.
• If you want a sneak peek at, or to start using, newer Python features before the full Python upgrade.

Changing division and print operations with future

Here's an illustrative use of __future__:

# Python 2 without __future__ - The times of integer division.
print(5 / 2) # Output: 2

# Python 2 with __future__ - Back to the future, where division got real.
from __future__ import division
print(5 / 2) # Output: 2.5
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And here's another:

# Python 2 without __future__ - Hanging on to the old-fashioned print statement.
print "Hello, World!"

# Python 2 with __future__ - Embracing the future with style!
from __future__ import print_function
print("Hello, World!")
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Forward thinking: Compatibility with future versions

As you step towards the future, keep in mind:

• Testing: Does your code behave as expected after importing with __future__?
• Code reviews: Are your __future__ imports necessary and correct? Discuss and review with your team.
• Documentation: Keep track of your __future__ imports to explain why you have chosen to use them.

Digging deeper: How future actually works

__future__ imports behave like compiler directives. They change the Python interpreter’s rules. What you should know:

• Up-to-date: You can find out when a __future__ feature was added and when it will become a default feature.
• Rules change: Normal imports just import code or functions. __future__ imports change the language rules itself. Yes, it's most certainly a rebel.
• Working with old code: Need to update that decades-old codebase? Use __future__ to get with the times without rewriting everything.

Notable future transitions

Some of the notable shifts experienced through __future__:

• nested_scopes: This was the time when inner functions got access to outer functions.
• generators: Introduced the yield keyword, lazy evaluation became a thing then.
• unicode_literals: Owing to __future__, Python 2.x started interpreting string literals as unicode, just as Python 3.x did.

Pushing the limits: Maximizing current interpreter value

By using __future__ imports, you essentially increase the value of your current Python interpreter by using newer features while remaining within the stable and tested ecosystem of your current Python version or software.

The future is now: Watch out for backward compatibility issues!

One thing to caution when going __future__ way: backward compatibility might take a hit. Bringing features from the future might make your code incompatible with older versions. Tread carefully, and preemptively manage deployment issues.