It is good practice to use meaningful variable names in a computer program. Say you used 'x' for time, and 't' for position, you or someone else will almost certainly make errors at some point.
If you do not use well-considered variable names:
- You're much more likely to make errors.
- When you come back to your program after some time you will have trouble recalling and understanding what the program does.
- It will be difficult for others to understand your program - serious program development is almost always a team effort.
Languages have rules for what characters can be used in variable names. As a rough guide, in Python variable names can use letters and digits, but cannot start with a digit.
Sometimes for readability it is useful to have variable names that are made up of two words. A convention is
to separate the words in the variable name using an underscore '_'. For example, a good variable name for storing the number of days would be
num_days = 10Python is a case-sensitive language, e.g. the variables 'A' and 'a' are different. Some languages, such as
Fortran, are case-insensitive.
Languages have reserved keywords that cannot be used as variable names as they are used for other purposes. The reserved keywords in Python are:
import keyword
print(keyword.kwlist)['False', 'None', 'True', 'and', 'as', 'assert', 'async', 'await', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'nonlocal', 'not', 'or', 'pass', 'raise', 'return', 'try', 'while', 'with', 'yield']
If you try to assign something to a reserved keyword, you will get an error.
Python 3 supports Unicode, which allows you to use a very wide range of symbols, including Greek characters:
θ = 10
α = 12
β = θ + α
print(β)22
Greek symbols and other symbols can be input in a Jupyter notebook by typing the LaTeX command for the symbol and then pressing the tab key, e.g. '\theta' followed by pressing the tab key.