A variable is a name that refers to a value, so you can store something now and use it
later. You create one with = — read it as “store this value in this name.” Run this, then
change "Ada" to your own name:
name = "Ada"
print(name)Ada
The name name now refers to the string "Ada", so print(name) shows it. Variables can
hold any value — a number, for example:
age = 36
print(age)36
And you can use several variables together:
first = "Ada"
last = "Lovelace"
print(first, last)Ada Lovelace
= means “store”, not “equals”This trips up almost everyone at first. In maths, = states a fact. In Python, = gives
an instruction: take the value on the right and store it in the name on the left. It
always flows right-to-left. That’s why a name can change — which is the next idea.
Assign a new value to the same name and it simply replaces the old one. The name always refers to whatever you stored in it most recently:
status = "loading"
print(status)
status = "ready"
print(status)loading ready
The best way to understand this is to watch it happen. Press Visualize and step through — notice how the value next to each name updates as the program runs:
player = "Sam"
score = 0
score = 50
score = 120
print(player, score)player stays "Sam" the whole time, while score is rebound three times until it
finally refers to 120.
Because Python figures out types as it runs, reassigning a variable can change its type
too. Remember type() from the last lesson? Watch it change:
data = 42
print(type(data))
data = "forty-two"
print(type(data))<class 'int'> <class 'str'>
A variable name must:
_),Score and score are different names).The common style in Python is snake_case — lowercase words joined by underscores:
user_score = 100
print(user_score)100
If you use a name you never assigned, Python doesn’t know it and stops:
print(total)NameError
Read it as “I’ve never heard of total.” The fix is to assign it first: total = 0.
NameError — the name
doesn’t exist yet.What does the = symbol do in Python?
Stores a value in a name (assignment) — = means "store this value in this name." It is an instruction, not a question. Checking equality is a different operator, ==, which you'll meet later.
After running score = 10 and then score = 25, what does print(score) show?
25 — Reassignment replaces the value. The name score refers to whatever was assigned to it most recently — 25.
Which of these is a valid variable name?
user_score — Names must start with a letter or underscore and contain no spaces. user_score is fine; 2nd_score starts with a digit, and "user score" has a space.
Are Score and score the same variable?
No — names are case-sensitive, so they are different — Python names are case-sensitive. Score and score are two completely separate variables.
Create a variable called planet that holds the text "Earth", then print it.
Use planet = "Earth" on one line, then print(planet) on the next.
planet = "Earth"
print(planet)Create a variable count set to 3. Then reassign it to 7. Then print count (it should show 7).
Assign 3 first, then assign 7 to the same name — the newer value wins.
count = 3
count = 7
print(count)