5 Tricky Python code snippets

 1. Misleading Variable Scope

This snippet demonstrates the tricky nature of variable scope in Python, particularly with nested functions.

def outer_function():

    x = "outer"

    def inner_function():

        nonlocal x

        x = "inner"

        print("Inner x:", x)

    inner_function()

    print("Outer x:", x)

outer_function()

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Inner x: inner

Outer x: inner

2. Mutable Default Arguments

This snippet shows the common pitfall of using mutable default arguments in function definitions.

def append_to_list(value, my_list=[]):

    my_list.append(value)

    return my_list

print(append_to_list(1))

print(append_to_list(2))

print(append_to_list(3))

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[1]

[1, 2]

[1, 2, 3]

3. Unexpected Behavior with Floating Point Arithmetic

Floating-point arithmetic can be non-intuitive due to precision issues.

a = 0.1

b = 0.2

c = 0.3

print(a + b == c)  

print(f"{a + b:.17f}")  

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False

0.30000000000000004

4. Changing a List While Iterating

This snippet demonstrates the pitfalls of modifying a list while iterating over it.

numbers = [1, 2, 3, 4, 5]

for i in numbers:

    if i % 2 == 0:

        numbers.remove(i)

print(numbers)

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[1, 3, 5]

5. Unpacking and Extended Unpacking

Python allows for complex unpacking operations which can be tricky to understand at first glance.

a, b, *c, d = range(6)

print(a)  

print(b)  

print(c)  

print(d)  

# Nested unpacking

x, (y, z) = (1, (2, 3))

print(x)  

print(y) 

print(z)  

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0

1

[2, 3, 4]

5

1

2

3