Don't pass mutable object to function as default value

default_mutable.py

"""
hollyandprosper.com
YouTube Channel: https://www.youtube.com/@hollyandprosper
Link to the original YouTube Short: https://youtu.be/lATMth5wb1E
"""

# wrong way

def add_tourist(tourist, tourist_list=[]):
    tourist_list.append(tourist)
    return tourist_list

# inspect

print(add_tourist("Andy"))
import inspect
sig = inspect.signature(add_tourist)
params = sig.parameters

for name, param in params.items():
    if param.default is not param.empty:
        print(f"{name}: {param.default}")

# correct way

def add_tourist(tourist, tourist_list=None):
    if tourist_list is None:
        tourist_list = []
    tourist_list.append(tourist)
    return tourist_list

print(add_tourist("Andy"))  
print(add_tourist("Bob"))