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GitHub Repository: pierian-data/complete-python-3-bootcamp
 Path: blob/master/00-Python Object and Data Structure Basics/01-Variable Assignment.ipynb
Views: 648
Kernel: Python 3

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Variable Assignment

Rules for variable names

  • names can not start with a number

  • names can not contain spaces, use _ intead

  • names can not contain any of these symbols:

    :'",<>/?|\!@#%^&*~-+

  • it's considered best practice (PEP8) that names are lowercase with underscores

  • avoid using Python built-in keywords like list and str

  • avoid using the single characters l (lowercase letter el), O (uppercase letter oh) and I (uppercase letter eye) as they can be confused with 1 and 0

Dynamic Typing

Python uses dynamic typing, meaning you can reassign variables to different data types. This makes Python very flexible in assigning data types; it differs from other languages that are statically typed.

my_dogs = 2

my_dogs
2
my_dogs = ['Sammy', 'Frankie']

my_dogs
['Sammy', 'Frankie']

Pros and Cons of Dynamic Typing

Pros of Dynamic Typing

  • very easy to work with

  • faster development time

Cons of Dynamic Typing

  • may result in unexpected bugs!

  • you need to be aware of type()

Assigning Variables

Variable assignment follows name = object, where a single equals sign = is an assignment operator

a = 5

a
5

Here we assigned the integer object 5 to the variable name a.
Let's assign a to something else:

a = 10

a
10

You can now use a in place of the number 10:

a + a
20

Reassigning Variables

Python lets you reassign variables with a reference to the same object.

a = a + 10

a
20

There's actually a shortcut for this. Python lets you add, subtract, multiply and divide numbers with reassignment using +=, -=, *=, and /=.

a += 10

a
30
a *= 2

a
60

Determining variable type with type()

You can check what type of object is assigned to a variable using Python's built-in type() function. Common data types include:

  • int (for integer)

  • float

  • str (for string)

  • list

  • tuple

  • dict (for dictionary)

  • set

  • bool (for Boolean True/False)

type(a)
int
a = (1,2)

type(a)
tuple

Simple Exercise

This shows how variables make calculations more readable and easier to follow.

my_income = 100
tax_rate = 0.1
my_taxes = my_income * tax_rate

my_taxes
10.0

Great! You should now understand the basics of variable assignment and reassignment in Python.
Up next, we'll learn about strings!