Epython Lab

The Bug That Taught Me More Than Any Tutorial

Last week, I ran into a bug that almost derailed a client demo.

A function that should have returned filtered results was quietly failing due to a simple logic oversight: an unintended mutable default argument in Python.

def get_filtered_data(filters=[]): # classic trap
...

Each call was modifying the default list, leading to unpredictable results. After debugging, I replaced it with:

def get_filtered_data(filters=None):
if filters is None:
filters = []
...

Takeaways:

Default mutable arguments in Python are a silent trap.

Writing tests isn't just a best practice—it’s your first line of defense.

Don’t just “write code that works”—write code that fails loudly and early when it breaks.


I’m sharing this because even experienced devs fall into these traps. The real lessons come from the messy, unpredictable parts of real-world coding.

Common mistakes of naming functions https://youtu.be/PY22gyHjLW8

www.tgoop.com/epythonlab/1961

987 viewsedited  Apr 7 at 13:06

The Bug That Taught Me More Than Any Tutorial

Last week, I ran into a bug that almost derailed a client demo.

A function that should have returned filtered results was quietly failing due to a simple logic oversight: an unintended mutable default argument in Python.

def get_filtered_data(filters=[]): # classic trap
...

Each call was modifying the default list, leading to unpredictable results. After debugging, I replaced it with:

def get_filtered_data(filters=None):
if filters is None:
filters = []
...

Takeaways:

Default mutable arguments in Python are a silent trap.

Writing tests isn't just a best practice—it’s your first line of defense.

Don’t just “write code that works”—write code that fails loudly and early when it breaks.


I’m sharing this because even experienced devs fall into these traps. The real lessons come from the messy, unpredictable parts of real-world coding.

Common mistakes of naming functions https://youtu.be/PY22gyHjLW8

BY Epython Lab