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

p = 10

p

10

l = 5

l

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!