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Python for Basic Data Analysis: 1.2 Variables

Get started on your learning journey towards data science using Python. Equip yourself with practical skills in Python programming for the purpose of basic data manipulation and analysis.

Variables

Variables

Variables are containers in which data values can be stored within the computer’s memory. They have a name, which is also referred to as an address. 


This is a box / container.
In variable terms, we can give it a name/address called box.

We can put things in the box. In programming, these things are called data values.

We can assign the data value books into the variable called box.
We use assignment operator  =  to assign the data value to the variable.


After assigning, we will have a box containing books.


By assigning a value into the box (variable), we can use the value multiple times by calling the box (variable), instead of retyping "books" (value).

Examples


box = "books"   The string value "books" is assigned to the variable box
block_number = 72 The number value 72 is assigned to (=) the variable block_number 
street_01 = ‘Nanyang Ave’ The string value ‘Nanyang Ave’ is assigned to the variable street_01
myList = ["apples", "bananas", "cherries"] The list of fruits are assigned to the bariable myList.

 Tip!  - It is good practice to choose meaningful / descriptive names that reflect the variable’s content for easier identification when you or someone else revisits your codes. Which variable names would you choose?

  • n = "Anna" or name = "Anna"
  • y = 2020 or year = 2020

Rules when assigning variable names
 

1. Must start with a letter, or the underscore character. 

  • Examples:    school             _company           address

2. Can only contain alpha-numeric characters and underscores.

  • (A to z)     _     (0 to 9)

3. Case-sensitive

  • name, Name and NAME are three different variables

4. Cannot contain hyphens.

5. Cannot start with a number.

6. Cannot use Python reserved words – these mean something in Python

False await else import pass
None break except in raise
True class finally is return
and continue for lambda try
as def from nonlocal while
assert del global not with
async elif if or yield

Exercises

1. Create a variable called fruit, and store "apple" into the variable you created and print. 

2. Are you able to print the following? Try it in your IDE. 

  1. 01_street = ‘Nanyang Ave’
  2. YEAR = 1995
  3. course_code = "DSE2020"
  4. my-birth-year = 1982
Questions Can it run? Changes
YEAR = 1995 Yes Nil
course_code = "DSE2020" Yes Nil
01_street = ‘Nanyang Ave’ No, variable names cannot begin with a number street_01 = 'Nanyang Ave'
my-birth-year = 1982 No, variable names cannot contain hyphens my_birth_year = 1982