6.1. Updating variables¶
Commonly, assignment statements are used to update a variable, where the new value of the variable depends on the old.
x = x + 1
This means “get the current value of x, add 1, and then
update x with the new value.”
If you try to update a variable that doesn’t exist, you get an error,
because Python evaluates the right side before it assigns a value to
x:
Before you can update a variable, you have to initialize it, usually with a simple assignment:
When you update a variable by adding 1 it’s called an increment; subtracting 1 is called a decrement.
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- The integer "2" prints.
- Incorrect! Take another look at the second line. Try again!
- We get a TypeError.
- Incorrect! This will not cause a TypeError because x, y, and 1 are all integers. Try again!
- We get a NameError.
- Correct! This will cause a NameError because x has not been initialized yet.
- The program compiles with no errors but nothing prints.
- Incorrect! This program will not compile. Try again!
Q-5: Consider the code block below. What happens when you run this program?
y = 1
x = x + 1
print(x)