Python has specific guidelines for naming variables to ensure clarity and avoid errors. These rules dictate what characters you can use and where you can position them within a variable name.
Start with a Letter or Underscore
⮞ The first character of your variable name must be a letter (a-z or A-Z) or an underscore (_).
⮞ This prevents confusion with numbers, which can't be the first character.
variable name examples
#Valid
name
_temporary_value
userAge (mixing uppercase and lowercase is allowed)
#Invalid
1variable (starts with a number)
$price (uses a special character other than underscore)
Alphanumeric Characters and Underscores Only
Once you start with a valid character, the remaining name can consist of letters (a-z or A-Z), numbers (0-9), and underscores.
This keeps variable names clear and concise.
valid and invalid variable names in python
#Valid
total_cost
user_input2
x1 (short variable names are acceptable for temporary values)
#Invalid
my-name (cannot use hyphens)
total@ (cannot use special characters other than underscore)
Case Sensitivity
Python treats variable names as case-sensitive. This means age, Age, and AGE are considered three different variables.
Be consistent with your casing to avoid unintended behavior.
Example:
Variable case sensitivity example to understand in python
age = 25
Age = 30
print(age)
print(Age)
Output
25
30
Reserved Words are Off-Limits
Python has a set of keywords reserved for specific language functions (like if, else, for, etc.). These keywords cannot be used as variable names.
You can find a list of reserved keywords
here.
Choosing Meaningful Names
While these rules ensure technical correctness, it's also crucial to choose descriptive variable names. Here are some tips:
⮞
Clarity is Key: Use names that reflect the variable's purpose. For example, customerName is clearer than x.
⮞
Descriptive Names: The longer the variable is used, the more important a clear name becomes.
⮞
Consistency: Maintain a consistent naming style throughout your code (e.g., snake_case for total_items).
Common Naming Conventions
⮞
Snake Case: Separate words with underscores (e.g., total_monthly_sales). This is the most popular convention in Python.
⮞
Camel Case: Capitalize the first letter of each word (e.g., totalPrice). This convention is less common in Python.
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