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Python Basics Literals and Variables

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Literals

Python Variables


Python can do any athematic calculations but to bring it to a meaningful representation, reusability and easy referencing a value we use variable.

Valid variable names


A variable name can be combination of letters, numbers, and underscore. The variable name must start with either letter or underscore symbol. No other symbol or numbers allowed in the first character.

Example variable names:

  
server_name
total_servers
cpu_load_average
server10_mem_size
The Variable name defined in lower case is different that defined with upper case, they are created at different memory locations.

  
cpu_load_average not same as CPU_load_average
mem not same as MEM

Invalid Variable definations


We should not use any type of operator symbols in defining the variable. Here is some variables defined throws errors 
  
c@paci+y ~ not valid @ and + 
total_@f_server ~ using @ not valid
10thserver ~ initial number not allowed  
Web Server load ~ spaces are not allowed instead we can use underscores
Note that variable name should not be use that is a datatype in Python example : int, float cannot be used.

In Python Variables defined in the following way:
  • The variables allow you to store values
  • A variable has a valid name (letters, digits, underscore, not a reserved keyword)
  • Python is dynamically typed that means variables can be redeclared/reassigned
  • We can use shortcut operators in order to cleanly redeclare a variable 
  • We can combine text and variables using the '+' operator in the print() function
print("Product cost:"+ product_cost)


The print() function


Comments in Python

As per my observation and learnings
  • Comments allows other developers in the team understand your code
  • A comment is created by a #followed by text
  • Do not write unnecessary comments in your python program write self document code that will be better
  • A multiline comment should have a hash in front of every line

The input() function

This input function is going  to prompt the user to get the data from the console.

The input function accepts an optional parameter that can be used in order to write message before the user inputs.

The input() method returns string value. So, if we want to perform arithmetic operations, we need to cast the value first.


How the print function is printing output, just opposite to that input() function reads the data in python.

Age =input("how old are you?")

In Python3, whatever you entered as input, the input() built-in function converts it into a string.

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