Packing and Unpacking

Packing and unpacking are incredibly convenient features in Python that allow you to group multiple values into a single collection, or extract values from a collection directly into individual variables.

Tuple Packing

Packing happens when you assign multiple values to a single variable without any brackets. Python automatically groups these values into a tuple.

# Packing three values into a single tuple
person = "Alice", 25, "Engineer"

print(person)        # ('Alice', 25, 'Engineer')
print(type(person))  # <class 'tuple'>

Basic Unpacking

Unpacking is the reverse process. It extracts elements from a collection (tuple, list, set, or string) and assigns them to multiple variables in a single line.

person = ("Alice", 25, "Engineer")

# Unpacking the tuple into three separate variables
name, age, profession = person

print(name)        # Alice
print(age)         # 25
print(profession)  # Engineer

Precaution: Variable Count Must Match

When doing basic unpacking, the number of variables on the left must exactly match the number of elements in the collection on the right.

numbers = (1, 2, 3)

# ERROR: Too many variables (expects 4 elements, got 3)
a, b, c, d = numbers  # ValueError: not enough values to unpack

# ERROR: Too few variables (expects 2 variables, got 3 elements)
x, y = numbers        # ValueError: too many values to unpack

Extended Unpacking with `*` (Starred Expression)

What if you only want to extract a few elements and group the rest together? Python lets you use the asterisk * operator to capture multiple elements.

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

# Capture the first element, and pack the rest into a list
first, *rest = numbers
print(first)  # 1
print(rest)   # [2, 3, 4, 5]

You can place the * variable anywhere:

# Capture the last element, pack the rest
*body, last = [10, 20, 30, 40]
print(body)  # [10, 20, 30]
print(last)  # 40

# Capture the first and last, pack the middle
first, *middle, last = "Python"
print(first)   # 'P'
print(middle)  # ['y', 't', 'h', 'o']
print(last)    # 'n'

Rule: You can only use one starred expression (*) in a single assignment. Otherwise, Python won’t know how to divide the elements, raising a SyntaxError.

Dictionary Unpacking with `**`

For dictionaries, you can use the double asterisk ** operator to unpack key-value pairs. This is commonly used to merge multiple dictionaries together.

default_settings = {"theme": "light", "notifications": True}
user_settings = {"theme": "dark", "font_size": 14}

# Merge dictionaries (user settings will override defaults)
merged_settings = {**default_settings, **user_settings}
print(merged_settings)
# Output: {'theme': 'dark', 'notifications': True, 'font_size': 14}

Unpacking in Loops

Unpacking makes iterating over complex data structures clean and readable.

1. Iterating over list of tuples/lists

pairs = [(1, "one"), (2, "two"), (3, "three")]

for number, name in pairs:
    print(f"{number} is spelled {name}")

2. Using `enumerate()`

The built-in enumerate() function returns pairs of (index, item), which you can unpack in the loop header:

fruits = ["apple", "banana", "cherry"]

for index, fruit in enumerate(fruits):
    print(f"Index {index}: {fruit}")

3. Iterating over dictionary `.items()`

ages = {"Alice": 25, "Bob": 30}

for name, age in ages.items():
    print(f"{name} is {age} years old")

Key Rules & Common Mistakes

ValueError: too many values to unpack

Happens when the number of elements on the right is greater than the number of variables on the left.

# Wrong
a, b = (1, 2, 3)  # ValueError!

# Fix: Use * to capture the rest
a, b, *rest = (1, 2, 3)

ValueError: not enough values to unpack

Happens when the number of variables on the left is greater than the number of elements on the right.

# Wrong
a, b, c = (1, 2)  # ValueError!

SyntaxError: two starred expressions in assignment

You cannot have more than one * variable on the left side.

# Wrong
*a, b, *c = [1, 2, 3, 4]  # SyntaxError!

Practice & Exercises

To reinforce what you’ve learned in this section (Tuple packing, basic unpacking, starred expression unpacking, and loop unpacking), practice with these interactive notebooks:

Follow-Along Practice

Practice packing values, basic unpacking, starred unpacking (*), and loop/dictionary merging.💻 VS Code | 🚀 Colab | 📥 Download

Practice Exercises

Test your knowledge with hands-on exercises on coordinate unpacking,Starred Marks partitioning, and configuration dictionary merging.💻 VS Code | 🚀 Colab | 📥 Download

What’s next?

Congratulations! You’ve completed Python Basics. Ready to start building programs?

Building Programs

Learn about functions

Python Foundations

Python Intermediate

Python Advanced

Tuple Packing

Basic Unpacking

Precaution: Variable Count Must Match

Extended Unpacking with `*` (Starred Expression)

Dictionary Unpacking with `**`

Unpacking in Loops

1. Iterating over list of tuples/lists

2. Using `enumerate()`

3. Iterating over dictionary `.items()`

Key Rules & Common Mistakes

Practice & Exercises

Follow-Along Practice

Practice Exercises

What’s next?

Building Programs

​Tuple Packing

​Basic Unpacking

​Precaution: Variable Count Must Match

​Extended Unpacking with * (Starred Expression)

​Dictionary Unpacking with **

​Unpacking in Loops

​1. Iterating over list of tuples/lists

​2. Using enumerate()

​3. Iterating over dictionary .items()

​Key Rules & Common Mistakes

​Practice & Exercises

Follow-Along Practice

Practice Exercises

​What’s next?

Building Programs

Tuple Packing

Basic Unpacking

Precaution: Variable Count Must Match

Extended Unpacking with `*` (Starred Expression)

Dictionary Unpacking with `**`

Unpacking in Loops

1. Iterating over list of tuples/lists

2. Using `enumerate()`

3. Iterating over dictionary `.items()`

Key Rules & Common Mistakes

Practice & Exercises

What’s next?