Assignment and Compound Operators
Assignment operators are used to assign values to variables. The most basic is the simple assignment operator (=), but Python also provides a suite of powerful augmented (or compound) assignment operators that combine an arithmetic or bitwise operation with assignment.
1. Simple Assignment (=)
The = operator assigns the value of the right-hand side expression to the left-hand side operand (a variable).
Assigning a single value to a variable.
Pyground
Assign your name to a variable and a dictionary to another.
Expected Output:
Name: Riya
Config: {'debug': True, 'version': 1.2}Output:
2. Sequence Unpacking
Assignment can also be used to “unpack” items from a sequence (like a list or tuple) into multiple variables.
The number of variables on the left must exactly match the number of items in the sequence.
Pyground
Unpack a user's name and role from a tuple.
Expected Output:
User 'Asha' has the role 'Admin'.
Output:
3. Augmented Assignment Operators
These operators combine an operation with an assignment, providing a more concise and often more efficient way to update a variable. For any operation op, x op= y is roughly equivalent to x = x op y.
Pyground
Track a running bank balance using augmented assignment for a series of transactions.
Expected Output:
Initial balance: $500.00 After deposit: $700.50 After withdrawal:$625.50
Output:
The In-Place Distinction
For mutable types (like lists and dictionaries), augmented assignments perform the operation in-place, modifying the original object. For immutable types (like numbers, strings, and tuples), they create a new object and reassign the variable.
This is one of the most important concepts related to assignment. Understanding it can prevent subtle bugs.
+= on a list modifies the original list. Any other variable pointing to that same list will see the change.
Pyground
Demonstrate how `+=` modifies a list in-place.
Expected Output:
Before: list_a is [1, 2], list_b is [1, 2] After: list_a is [1, 2, 3, 4], list_b is [1, 2, 3, 4]
Output:
4. Assignment Expressions (The “Walrus Operator” :=)
Introduced in Python 3.8, the walrus operator := allows you to assign a value to a variable as part of a larger expression. It’s useful for simplifying loops where you need to compute a value and then check it.
Pyground
Read lines from a list until an empty line is found, processing each line as you go.
Expected Output:
Processing: 'first line' Processing: 'second line' Done.
Output:
Use the walrus operator sparingly to improve clarity in specific patterns like the while loop above. Overuse can make code harder to read.