Python Variables

Veriables are used to tag the data. They act as reference for data or objects.

Creating Variables

Python is implicitly defined hence creating variable only requires:
1. Variable Name
2. '=' : assignment operator
3. Value

variable = value

a = 1 # int
b = 1.3 # float
c = 1+2j # complex
d = "hello" # str
e = [1, 2, 3, 2] # list
f = (1, 2, 3, 2) # tuple
g = {"a": "apple"} # dict
h = {1, 2, 3} # set

Variable Nomenclature

A variable name must obey all three rules in Python:

  1. It must consist of only A-Za-z0-9_
  2. It must not begin with digits 0-9
  3. It must not be a keyword. import keyword; print(keyword.kwlist)
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Assignment Operator

= is used as assignment operator whereas == is used for comparision. = works right-side to left-side in a code statement.

LHS ← RHS

Multiple assignment

Python allows for multiple values to be assigned multiple variable references in the same statement.

x, y, z = 1, 2, 3
x = y = z = 0

type() function

type(object) takes a variable or an object and returns its object type.

>>> x = "hello"
>>> type(x)
str

Input/Output Variable

A builtin input() provides a consoole interface for any input value. The default data type is str.
For publishing a value from variable reference simply use the builtin function print().

>>> x = input("Enter something: ")
>>> print(x)

Type casting

eval() function can evaluate any value to its correct data type. Formatting is required such as string must use quotes and list must use [] etc.
Apart from eval() function the respective data type function can also be used for type casting. Eg: int(), float(), complex(), str(), list(), tuple(), dict(), set()

>>> x = input()
1
>>> type(x)
str

>>> x = eval(input())
1
>>> type(x)
int

Python Global Variable

Variables that are defined outside any function definition and directly under the module namespace are called global. The scope of global variables is the entire module.


Python Global Variable