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If a software language is easy in terms of declaring variables, then consider that half of the time and effort are saved. Python is one of the easiest and most convenient languages for declaring variables. We will dive deep into the variables of Python, their rules of declaration, and basic information about variables.

Basic Data Types

• Integers
• Floating-Point numbers
• Strings
• Complex number
• Boolean Type

1. Declaring variables and assigning variables

• Many Languages like c++, Java and c need us to declare a variable before using it.
• Python does not require the declaration of variables to a certain data type. Just assigning a variable is enough to declare it.
• To assign a Variable, we simply need to use the = operator.

# Declare string 
name='john doe'
name

'john doe'

# Declaring integer
num=5
num

5

# Declaring Float
pi=3.14
pi

3.14

2. Variable names

What to consider before naming variables?

Rule 1: Variable names must not start with numbers.

 # declare variable five
 five=5
 print(five)

5

# declare variable f5
f5=5
print(f5)

5

Rule 2: Variable names must not include these special symbols.

, < > / + @ – ‘ “” : ? # % ^ & * ~ | \ !

# using special symbol & in variable.
jacknjill='hill'
# using special symbol @ in variable.
johndoemail='johndoe@gmail.com'

print(jacknjill)
print(johndoemail)

hill
johndoe@gmail.com

Rule 3: Names cannot contain spaces; use _ instead.

# avoid using special symbol @ in variable.
john_doe_at_age=20
# use _ instead of blank spaces.
john_doe_age=20

print(john_doe_at_age)
print(john_doe_age)

20
20

Rule 4: Variable names must not contain Python’s keywords.

# Don't use a keyword for a variable.
if=5

  File "<ipython-input-9-5719a260f2d6>", line 2
    if=5
      ^
SyntaxError: invalid syntax

3. Multiple assignments

• Python allows the assignment of multiple variables at the same time.

# Assign multiple variables the same value at once.
d=e=f=110
print(d)
print(e)
print(f)

110
110
110

4. Type Casting

• Python allows typecasting.
• Typecasting is a way to change the datatype of a variable.

pi=3.14 # Store value of pie in pi
print(pi)

3.14

# print type of pi
type(pi)

float

Let’s change pi’s datatype to an integer with int().

# type cast pi into integer
int(pi)

3

Let’s convert a number stored in string format to an integer with int().

# store string in alphabets
alphabets='6798'
print(alphabets)
print(type(alphabets))


# typecast alphabets into integer.
int(alphabets)

6798
<class 'str'>
6798

5. Python variable types

• Local
• Global

Local Variable

Let’s explain the local variable with a simple function.

# element1 is global variable.
# element2 is local variables in the chemist function.
element1 = "methane"
def chemist():
  element2 = "ethane"
  element2 = element2 + element1
  
  
  print(element2)


chemist()

ethanemethane

As you see above, the variable element1 is declared above the scope of chemist(), so it is available to all child
scopes in it.

Element2 is declared in the chemist() function, so it is exclusive to the chemist() and its child scopes only.

print(element1)

methane

If you try to access local variables outside their scope, this error will occur, but element 1 is accessed in the function despite being in a different scope. Because it was accessed within its sub-scope. You can access the variables from the parent scopes.

Global variable

There is a way to access the local scope variables outside the scope. If we declare the local variables as global with a global keyword.

# element1 is global variable.
# element2 is local variables in the chemist function.
element1 = "methane"
def chemist():
  global element2
  element2 = "ethane"
  
  element2 = element1 +  element2
  
  
  return element2

chemist()
print(element2)

methaneethane

# accessing element2 has been made global
print(element2)


# access the local variable through chemist() function.
print(chemist())

methaneethane

methaneethane

As you can see above, if you declare a variable with the global keyword, it becomes accessible in all scopes. Be careful with using global; it may create discrepancies in the security of working systems.

6. Delete a variable

You can delete a variable in Python by using the ‘del' keyword.

Syntax: del variable_name

#store value of pie
pie=3.146
print(pie)

3.146

# delete pie 
del pie
%who pie

No variables match your requested type.

In the above code, we used %who pie to find the deleted variable.