Python Variable Names

Learn the rules for naming variables in Python, including starting with a letter or underscore, avoiding starting with a number, and ensuring names are case-sensitive and do not conflict with Python keywords.

Variable Names in Python

In Python, a variable can have a short name (like x and y) or a more descriptive name (like age, carname, or total_volume). Here are the rules for naming variables in Python:

  • A variable name must start with a letter or the underscore character (_).
  • A variable name cannot start with a number.
  • A variable name can only contain alphanumeric characters and underscores (A-z, 0-9, and _).
  • Variable names are case-sensitive (e.g., age, Age, and AGE are three different variables).
  • A variable name cannot be any of the Python keywords.
Example

Legal Variable Names


        myvar = "Alice"
        my_var = "Bob"
        _my_var = "Charlie"
        myVar = "David"
        MYVAR = "Eve"
        myvar2 = "Frank"
        
        
        print(myvar)
        print(my_var)
        print(_my_var)
        print(myVar)
        print(MYVAR)
        print(myvar2)
Output

        Alice
        Bob
        Charlie
        David
        Eve
        Frank
Example (with Syntax Error)

Illegal Variable Names


2myvar = "Alice"
my-var = "Bob"
my var = "Charlie"
Error Output:

Traceback (most recent call last):
  File "/usr/lib/python3.8/py_compile.py", line 144, in compile
    code = loader.source_to_code source_bytes, dfile or file,
  File "", line 846, in source_to_code
  File "", line 219, in _call_with_frames_removed
  File "./prog.py", line 1
    2myvar = "Alice"
     ^
SyntaxError: invalid syntax

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "", line 1, in 
  File "/usr/lib/python3.8/py_compile.py", line 150, in compile
    raise py_exc
py_compile.PyCompileError:   File "./prog.py", line 1
    2myvar = "Alice"
     ^
SyntaxError: invalid syntax

Remember that variable names are case-sensitive.

Multi-Word Variable Names

Variable names with more than one word can be difficult to read. There are several techniques to make them more readable:

Camel Case

In Camel Case, each word, except the first, starts with a capital letter:

Example

myVariableName = "Alice"

Pascal Case

In Pascal Case, each word starts with a capital letter:

Example

MyVariableName = "Bob"

Snake Case

In Snake Case, each word is separated by an underscore:

Example

my_variable_name = "Charlie"