This Python Variables lesson is for a beginner. Read the short notes, run each example, then change one name or number and run it again.
A variable is a name attached to a value. You create it by writing the name, an equals sign, and the value. Python has no separate declare step, and you do not write the type in front of the name.
The value still has a type. Text is str, a whole number is int, a decimal is float, and True or False is bool. One name can later hold a different type. The new assignment replaces the old value.
type() shows the type of the value stored right now. str(), int(), and float() build a new value of the type you ask for. The text "24" and the number 24 are not the same.
Names are case-sensitive, so city and City are two variables. Text can use single quotes or double quotes. Both produce str.
Example 1: Start here
The = sign creates the variable. Words after # are a note for you. Python skips them and still runs the code.
city = "Chennai" # text, type str
seats = 24 # whole number, type int
print(city)
print(seats)
Example 2: The type can change
label starts as a whole number. The comment after # says int. The next assignment stores text, so the same name is now str. Python does not run the comment.
label = 24 # label is type int
print(label, type(label)) # type() shows what kind of value this is
label = "full" # label is now type str
print(label, type(label)) # type() shows what kind of value this is
Example 3: Text, numbers, and yes or no
Each comment names the type stored on that line. course is text, seats is a whole number, fee has a decimal point, and open_batch is True or False.
course = "Python" # str, text
seats = 24 # int, whole number
fee = 24999.50 # float, decimal
open_batch = True # bool, yes or no
print(type(course)) # type() shows what kind of value this is
print(type(seats)) # type() shows what kind of value this is
print(type(fee)) # type() shows what kind of value this is
print(type(open_batch)) # type() shows what kind of value this is
Example 4: Convert with casting
str() makes text, int() reads a whole number, and float() keeps a decimal. The # note tells you which conversion that line does.
seats_text = str(24) # int becomes text
seats = int("24") # text becomes int
fee = float(24) # int becomes 24.0
print(seats_text, type(seats_text)) # type() shows what kind of value this is
print(seats + 1)
print(fee)
Example 5: Single quotes or double quotes
Both quote styles store text. The comparison prints True because the letters match.
name_a = "Asha" # double quotes, still str
name_b = 'Asha' # single quotes, still str
print(name_a == name_b) # a comparison is True or False
print(type(name_a), type(name_b)) # type() shows what kind of value this is
Example 6: Names are case-sensitive
city and City are not the same name. Changing City does not change city.
city = "Chennai" # lowercase name
City = "Pune" # different variable
print(city)
print(City)
Example 7: Print a variable in a sentence
The first print mixes text and a number with commas. The second joins text only, so str() converts the number first.
course = "Python" # text
seats = 24 # a whole number
print(course, "has", seats, "seats") # comma accepts the number
print(course + " has " + str(seats) + " seats") # plus needs text
Example 8: One name can hold many values
Square brackets make a list. Curly braces make a dictionary. Each one is still a single variable.
skills = ["Python", "SQL"] # list, ordered values
scores = {"Asha": 82, "Arun": 74} # dict, name and number
print(type(skills)) # type() shows what kind of value this is
print(type(scores)) # type() shows what kind of value this is
print(skills[0])
print(scores["Asha"])
