Note the following examples:
```python
x = 6
x = 6 + 1
# x is now assigned to 7
```
```python
x = 5
x = 6
#x is now assigned to 6
x += 1
#x is now assigned to 7
x -= 1
#x is now assigned back to 6
```
```python
totalbalance = 100
directdeposit = 50
totalbalance = totalbalance + directdeposit
print(totalbalance) #Result is 150.
```

How to update variables in Python 

After setting variables, their assigned values can be updated through the use of operators. If the print() function is applied to the reset variable, the newly updated value will appear. 

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A variable is where data values can be stored. Another way to say this is that a value can be referred to by its respective variable. Variables do not need to be declared with any particular type, and can even change type after they have been set.

Variables in Python

- Expressions are any combination of data types to be evaluated. Evaluating an expression results in values/objects. Expressions can also be evaluated into or set to values. 
- Asking Python to print an expression will result in the interpreter attempting to evaluate the expression and display the result

Expressions in Python 

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Runestone: Foundations of Python Programming

Variables, which store values, can have names of any length, but variables named with the following will be considered invalid:
- Have spaces 
- Start with numbers
- Possess illegal characters (i.e. $)
- Is a Python Keyword

As long as the variable name does not possess any of the above characteristics, it will be valid. 


Rules for Naming Variables 

Use the equal sign ("=") with the variable name on the left and the value on the right. 

Examples:
- car_model = "Ford Taurus"
- Total_Cost = 400
- n = 18

Note that the equal sign does not mean "equal to" in this case. It should be read as "(Variable) refers to (Value)." For example, "n refers to 18." 

Setting Variables in Python 

Updating Variables in Python 

Hard Coding is the practice of writing code that can only satisfy one solution. While the hard-coded variable may be correct in a given circumstance, the overall logic of the code is not validated. 

The logic, flow, and computations should be depended on when writing code.

Why Not to Hard Code When Learning Python

- 7 * 6
- 5 / 3
- 1429
- print("Hello World!") 
- print(add(square(x), square(y)))
- len("What's up, man?") 

Examples of Expressions in Python 

A common programming exercise involves writing a program to calculate the sum of the squares of numbers in a given list. For instance, given the list of numbers [2, 10, -9, 78], the task is to compute the value of $2^2 + 10^2 + (-9)^2 + 78^2$.

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