Python function global variables?

Three pillars of global variables

Functional chronology: The order of the universe

In the cosmos of Python, neither time nor the spatial arrangement of functions impact the behavior of the variable. But the order of invoking functions plays a key role in determining the current state of a global variable. Call a function after the global variable is staged for the play!

Mutating or re-binding: An existential crisis

Finding life too mundane? How about re-binding an old name to a new identity? In Python drama, before your function can venture on such an audacious endeavor, it needs the global keyword.

“Mutation”, on the other hand, might sound very sci-fi, but it's as easy as changing your gloves in Python. List, dict - all enjoy this privilege, and you don't need "global" for that.

team = ["Harry", "Hermione", "Ron"]

def add_to_team():
    team.append("Dumbledore")  # Old team gets a magical upgrade, without using "global"

add_to_team()
print(team)  # Outputs: ["Harry", "Hermione", "Ron", "Dumbledore"]
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Default parameters: An autobiography traced backward in time

Here's an open secret: In Python, default parameters capture a snapshot of their default values at the point of function definition. And mind you, they don't give a mushroom about whether your global variables have evolved since then:

year = 2001

def magicHappened(harry_born=year):  # Harry's birth year is stored at function definition
    print(harry_born)

year = 2021
magicHappened()  # It still prints: 2001, oblivious to current year!
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To infuse dynamism in default parameters, let's enlist the help of None and set it ringing inside the function:

year = 2001

def magicHappened(harry_born=None):
    if harry_born is None:
        harry_born = year
    print(harry_born)

year = 2021
magicHappened()  # Now prints: 2021, welcoming the magic of the current year!
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When globals go wild!

'Global' in Python: A tool or a trap?

To ensure the maintainability of code, always use global variables with caution and contextual relevant. They are not necessarily the villains they are often made out to be, but using them inappropriately can lead to code denser than a black hole!

Breathing life into dead code

Unsystematic use of global variables can lead to zombie code, which defies logic and feeds upon your peace of mind! Hence, prioritize readability and simplicity.

Code aesthetics: Apply the GOLDen rule

Prefer the use of local variables and function parameters. When the need arises to leverage global variables, G: Get Prudent, O: Optimize Usage, L: Leverage Locals, and D: Do Simplify. Total GOLD!

Requires a safety net

Global variables are like jugglers, they can perform exceptional tasks but also create big trouble when things go sideways!

Mind the scope

Ensure no naming conflicts arise between global and local variables with the same names.

Attempting alternatives

Analyze and explore alternatives before settling for global variables. They aren't your only saviors!

Quality assurance: Test, test, and test!

It holds ground for everything, and global variables are no exception. Test your approaches, scenarios, and contexts. Remember, thorough testing saves a lot of heartache!