Python For Beginner's Day - 3

Python Variables

• It is a reserved memory location to store the data values.

  Creating Variables:

• A Variable is created, when a value is assigned to it.

  

  

• Variables are not required to be declared with any particular type and can be changed after they have been set.

  

  

• If a variable data type to be specified, that can be done by Casting.

  

  

• To get the type of the variable, use type() function.

  

  

• String Variables can be declared either by using Single or Double Quotes.

Variable Names

• are case-sensitive(a, A are 2 different variables)

• can have a short name like x, y.... or it can be a descriptive like firstname, age, ...

• must start with underscore(_) or a letter and can contain alpha-numeric characters and _ (A-Z, a-z, 0-9 and _).

• cannot start with number.

• cannot be any of Python Keywords.

• Legal Variable Name Declaration:

• Illegal Variable Name Declaration:

• Multi word variable names can sometimes be difficult to read. So those can be written in

  • Camel Case: Each word except the first, starts with capital letter. Eg: varName = "Sita"

  • Pascal Case: Each word starts with Capital letter. Eg: VarName = "Sita"

  • Snake Case: Each word is separated by an underscore(_). Eg: var_name = 'Sita'

Assign Multiple Values:

• Values can be assigned to multiple variables in one line.

  Eg:

• 

  NOTE : Make sure the number of variables assigned should match the number of values.

• Single Value can be assigned to multiple variables in one line.

  Eg:

  

• If there is a collection of values in a list, these values can be extracted to variables. This is called as unpacking.

  Eg:

  

Output Variables - print() Function

• As we already saw in our examples above, print() is used to output variables.

• It can also be used to output multiple variables, separated by comma(,) or using + operator.

  

  

• + operator works as mathematical operator for integers.

  NOTE: By using + operator, it's not possible to combine string and integer. Instead, separate with commas which supports with any data type.

  Global Variables:

• can be used both inside and outside the function.

  

  

• If the same variable is created inside the function, then it is called a local variable and can be used inside the function. The global variable with same name remains as it is and with the original value.

  

  

'global' Keyword:

• As seen above about local variable, in order to make that as global inside the function use 'global' keyword.

• Also, to change the value of global variable inside the function.