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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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 

This website offers a guide on how Python code should be formatted: https://www.python.org/dev/peps/pep-0008/

PEP 8 Style Guide

- 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

This is a list of Python keywords that cannot be 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_```



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