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Python Variables

  • Variables are containers for storing data values.

  • There is no any concept  for declaring a variable in python unlike other programming languages.

  • A variable is created the moment you first assign a value to it.

How to Declare and use a Variable

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Python variable defined using simple ways like you can see it below given example and print it–

>>> a = 5

>>> print(a)

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You can get result 5.

Concatenate Variables

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We can concatenate Variables using below given logic:

>>> a = 5

>>> b = 4

>>> print(“The Result is”, str( a)+ “” +str(b))

Naming convention of Variable in python

A variable can have a short name (like x and y) or a more descriptive name (name, age, gender, carname, total_average).

 

Rules for Python variables:

  • A variable name must start with a letter or the underscore character

  • A variable name cannot start with a number

  • A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ )

  • Variable names are case-sensitive (age, Age and AGE are three different variables)

The common naming styles in Python code and when you should use them:

  • Variable: Use a lowercase single letter, word, or words. Separate words with underscores to improve readability.   Example: x, var, my_variable

  • Constant: Use an uppercase single letter, word, or words. Separate words with underscores to improve readability. Example: PI, MAX_VALUE, MIN_VALUE

  • Function: Use a lowercase word or words. Separate words by underscores to improve readability. Example: display, show, my_function

  • Class: Start each word with a capital letter. Do not separate words with underscores. This style is called camel case. Example: Employee, Student, Person, Model, MyClass

  • Module: Use a short, lowercase word or words. Separate words with underscores to improve readability. Example: module.py, my_module.py

  • Package: Use a short, lowercase word or words. Do not separate words with underscores.Example: package, mypackage

Assign Value to Multiple Variables once in one line

  •  Assign different values to multiple variables in one line:

x, y, z = 5 ,10 ,15
print(x)
print(y)
print(z)

  •  Assign same value to multiple variables in one line:

x, y, z = 10
print(x)
print(y)
print(z)

Global Variables

Global variable is used to access command value through out the program. Global variable can be accessed from inside or outside from function, class or methods.  

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Global variable in python can be defined by two ways:

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  • Without global keyword.

  • Using global keyword.

  1. Without global keyword

college_id = 10

def myfunc():
  print("Python is " + college_id)

myfunc()

Note: Always try to define global variable top line of program so that rest of the code after that can use it.

 2. Using global keyword

def myfunc():

     global college_id 

     college_id = 10
 
myfunc()

print("Python is " + college_id)

What will happen If you create a variable with the same name inside a function

college_id = 10

def myfunc():

    college_id = 20
    print("Id inside function " + college_id)

myfunc()

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print("Id outside function " + college_id)

Output:

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Id inside function  20

Id outside function  10

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local value will be used if we create variable with the same name as global

Thanks for reading this, In the next tutorial, we will learn about “python data types”

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