In the previous tutorial you learned about Python comments. Now, let's learn about variables and literals in Python.
Python Variables
In programming, a variable is a container (storage area) to hold data. For example,
number = 10
Here, number is a variable storing the value 10.
Assigning values to Variables in Python
As we can see from the above example, we use the assignment operator = to assign a value to a variable.
# assign value to site_name variable
site_name = 'programiz.pro'
print(site_name)
# Output: programiz.pro
Output
programiz.pro
In the above example, we assigned the value programiz.pro to the site_name variable. Then, we printed out the value assigned to site_name
Note: Python is a type-inferred language, so you don't have to explicitly define the variable type. It automatically knows that programiz.pro is a string and declares the site_name variable as a string.
Changing the Value of a Variable in Python
site_name = 'programiz.pro'
print(site_name)
# assigning a new value to site_name
site_name = 'apple.com'
print(site_name)
Output
programiz.pro apple.com
Here, the value of site_name is changed from 'programiz.pro' to 'apple.com'.
Example: Assigning multiple values to multiple variables
a, b, c = 5, 3.2, 'Hello'
print (a) # prints 5
print (b) # prints 3.2
print (c) # prints Hello
If we want to assign the same value to multiple variables at once, we can do this as:
site1 = site2 = 'programiz.com'
print (x) # prints programiz.com
print (y) # prints programiz.com
Here, we have assigned the same string value 'programiz.com' to both the variables site1 and site2.
1. Constant and variable names should have a combination of letters in lowercase (a to z) or uppercase (A to Z) or digits (0 to 9) or an underscore (_). For example:
snake_case
MACRO_CASE
camelCase
CapWords
2. Create a name that makes sense. For example, vowel makes more sense than v.
3. If you want to create a variable name having two words, use underscore to separate them. For example:
my_name
current_salary
5. Python is case-sensitive. So num and Num are different variables. For example,
var num = 5
var Num = 55
print(num) # 5
print(Num) # 55
6. Avoid using keywords like if, True, class, etc. as variable names.
Python Literals
Literals are representations of fixed values in a program. They can be numbers, characters, or strings, etc. For example, 'Hello, World!', 12, 23.0, 'C', etc.
Literals are often used to assign values to variables or constants. For example,
site_name = 'programiz.com'
In the above expression, site_name is a variable, and 'programiz.com' is a literal.
There are different types of literals in Python. Let's discuss some of the commonly used types in detail.
Python Numeric Literals
Numeric Literals are immutable (unchangeable). Numeric literals can belong to 3 different numerical types: Integer, Float, and Complex.
1. Integer Literals
Integer literals are numbers without decimal parts. It also consists of negative numbers. For example, 5, -11, 0, 12, etc.
2. Floating-Point Literals
Floating-point literals are numbers that contain decimal parts.
Just like integers, floating-point numbers can also be both positive and negative. For example, 2.5, 6.76, 0.0, -9.45, etc.
3. Complex Literals
Complex literals are numbers that represent complex numbers.
Here, numerals are in the form a + bj, where a is real and b is imaginary. For example, 6+9j, 2+3j.
Python String Literals
In Python, texts wrapped inside quotation marks are called string literals..
"This is a string."
We can also use single quotes to create strings.
'This is also a string.'
More on Python Literals
There are two boolean literals: True and False.
For example,
is_pass = True
print(is_pass)
# Output: True
Here, True is a boolean literal assigned to is_pass.
Character literals are unicode characters enclosed in a quote. For example,
some_character = 'S'
Here, S is a character literal assigned to some_character.
Python contains one special literal None. We use it to specify a null variable. For example,
value = None
print(value)
# Output: None
Here, we get None as an output as the value variable has no value assigned to it.
Let's see examples of four different collection literals. List, Tuple, Dict, and Set literals.
# list literal
fruits = ["apple", "mango", "orange"]
print(fruits)
# tuple literal
numbers = (1, 2, 3)
print(numbers)
# dictionary literal
alphabets = {'a':'apple', 'b':'ball', 'c':'cat'}
print(alphabets)
# set literal
vowels = {'a', 'e', 'i' , 'o', 'u'}
print(vowels)
Output
['apple', 'mango', 'orange']
(1, 2, 3)
{'a': 'apple', 'b': 'ball', 'c': 'cat'}
{'e', 'a', 'o', 'i', 'u'}
In the above example, we created a list of fruits, a tuple of numbers, a dictionary of alphabets having values with keys designated to each value and a set of vowels.
To learn more about literal collections, refer to Python Data Types.