Keywords are special, built in words in a programming language that can only be used in certain ways. They often have specific values or functions and cannot be used to name new variables or functions. Many IDEs will highlight keywords in order to differentiate them from the rest of the code. 

Python Keywords

This is a list of Python keywords that cannot be variable names.

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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 

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- my_name
- price_of_tea_in_france
- Go_Blue
- H1s_nam3_1s_bob

Examples of Valid Variable names

- 76trumpets
- 1_love_pandas
- car$
- lambda
- false 
- Give_me_an_A+ 
- Total Cost 
- Six*7

Examples of Invalid Variable Names

List of Python Keywords 

There are further conventions for naming variables:

-If you are naming something with multiple words, use the underscore character in place of spaces, i.e. ```average_number```

-If you want to use a variable name that is the same as a Python Keyword, place the underscore character after the variable, i.e. ```list_```



Additional Naming Conventions

In Python Programming, it is customary to give constants an all-caps variable name in order to help others looking over the code. Take an example where we are using a ```for``` loop to calculate the average value in a list of 20 values.
```python
average=0
for i in values:
   average+=(i/20)
```
In this example, it is unclear where we got the 'magic constant' 20. However, if we use Python Style Guidelines:
```python
average=0
NUM_VALS=20
for i in values:
   average+=(i/NUM_VALS)
```
In this second example, it is more explicit what the numbers are doing within the operation. Thus, this is the preferred way to deal with constants in Python.

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