Once a variable exists, you can give it a new value at any time — just write the variable name and a new value. No let or special keyword needed in Python.
Reassigning a Variable
Demo
health =100
print(health)
health =50
print(health)
Demo
100
50
Self-Referential Updates
A variable can even appear on both sides of the = sign. Python evaluates the right side first using the old value, then stores the result as the new value.
Self-Referential Updates
Demo
health =100
print(health)
health = health -20
print(health)
Demo
100
80
A Common Mistake
Beginners often write the calculation and forget to store it. Python works out the answer, then throws it away — and there is no error message to tell you.
A Common Mistake
Demo
health =100
print(health)
❌health -20
print(health)
Demo
100
100
Nothing changed. Without the health = in front of it, the new value has nowhere to go.
Today's Objectives
Reassigning a variable's value
Updating a variable based on its own current value
Tracking a value as it changes over time
Key Terms
Reassignment
Giving an existing variable a new value.
Self-Referential Update
An assignment where a variable's current value is used to compute its new value, like health = health - 20.
State
The current value(s) a program is keeping track of at a given moment.
'F' → Fullscreen
Build
Create a new Python program named 1-5-reassignment.
Task 1: Start With a Value
Create a health variable set to 100 and a score variable set to 0.
Print each variable with a label.
Variable Reassignment
1
health =100
2
score =0
3
4
print("Health:", health)
5
print("Score:", score)
6
#
Task 2: Take Damage
Reassign health to itself minus 30.
Print the updated value with a label.
Variable Reassignment
1
health =100
2
score =0
3
4
print("Health:", health)
5
print("Score:", score)
6
7
health = health -30
8
print("Health:", health)
9
#
Task 3: Earn Points
Reassign score to itself plus 50, then print it.
Reassign score to itself plus 25 a second time, then print it again.
Variable Reassignment
1
health =100
2
score =0
3
4
print("Health:", health)
5
print("Score:", score)
6
7
health = health -30
8
print("Health:", health)
9
10
score = score +50
11
print("Score:", score)
12
13
score = score +25
14
print("Score:", score)
15
#
Challenge (Optional): Heal Up
Reassign health one more time to represent healing (add some points back), then print the updated value.
Compare the final value to the value you started with.
Checkpoint
Verify your program works correctly.
Example Output
Health: 100
Score: 0
Health: 70
Score: 50
Score: 75
Reflection
Answer the following questions before submitting your work.
In Python, making a brand new variable and giving an existing one a new value look identical — both are just health = something. What is different about what Python does the second time?
In health = health - 30, which value does Python use to compute the right side of the = — the old value or the new value?
Why might a program need to update the same variable more than once while it's running?
Submit
Submit the required files to the appropriate dropbox.
