9 Confusing Python Concepts That Frustrate Most Developers

1. The is vs == Confusion

== compares values (equality), while is compares object identities (whether two objects point to the same memory location).

a = [1, 2, 3]
b = [1, 2, 3]
print(a == b)  
print(a is b)

True
False

2. Mutable Default Arguments

Using mutable objects (like lists or dictionaries) as default arguments in function definitions leads to unexpected behavior.

def add_element(element, my_list=[]):
    my_list.append(element)
    return my_list

print(add_element(1))  
print(add_element(2))

[1]
[1, 2]

3. Indentation Sensitivity

Python’s strict use of whitespace for block definition can be a challenge for new users. Inconsistent or invisible tabs vs spaces can cause errors.

In [7]:

if True:
    print("Hello")
    print("World")

Hello
World

4. The GIL (Global Interpreter Lock)