What Variable Names Are Illegal in Python?

Excerpt

Discover the restrictions on variable names in Python and why choosing the right variable names is essential for effective programming. Explore the valid and invalid variable names, specific restrictions in Python, and best practices for selecting meaningful and descriptive names.

Python has specific rules and conventions for naming variables. Using illegal names can cause errors or make your code hard to understand. In this article, we’ll cover what makes a variable name invalid in Python.

Introduction

In Python, variables hold values or references to objects. You need to assign them unique names adhering to Python’s syntax and style rules.

Proper naming is important because it makes code more readable. Illegal names will generate errors or confuse those reading your code later on.

Syntax Restrictions

Python has some syntax restrictions on variable names:

No Spaces or Symbols

Variable names cannot contain spaces, quotation marks, or other symbols like @ and %. The only symbol allowed is the underscore _.

To separate words in a variable name, use underscores. This snake_case style is standard in Python. Tools like String_to_Snake_Case help format strings into this format.

Length Limit

Python variable names cannot exceed 253 characters. Excessively long names over this limit can cause issues.

Starts with Letter or Underscore

The name must begin with an underscore or letter. Starting with a number or other symbol will cause an error.

Avoid Python Keywords

You cannot use Python keywords and built-in identifiers as variable names. These words are reserved in Python:

1and       del       from      None      True
2as        elif      global    nonlocal  try
3assert    else      if        not       while
4break     except    import    or        with
5class     False     in        pass      yield
6continue  finally   is        raise
7def       for       lambda    return

Tools like String_to_Lowercase help avoid accidentally using reserved words as names.

Stylistic Conventions

Python also has some standard naming conventions to follow:

snake_case Over CamelCase

Variable names should use snake_case like my_variable instead of CamelCase or PascalCase.

Use String_to_CamelCase When Needed

However, if interface with other languages that use CamelCase, you can use tools like String_to_CamelCase to convert names.

Readability

Even if a name follows syntax rules, it can still be illegal if it harms readability:

Be Descriptive

Names should describe the value or purpose of the variable. Generic names like data or temp are vague.

Full Words Over Abbreviations

Avoid short abbreviations that are unclear like cnt or stmt_cnt. Write out full words for readability.

Use String_to_Capital Carefully

You can capitalize the first letter of words with String_to_Capital to distinguish internal words, like maxStudentCount. But use this sparingly.

Examples of Illegal Names

Here are some examples of illegal variable names in Python:

Cannot Contain Spaces

1my variable = 5 # Illegal, spaces invalid

Cannot Begin With Number

11value = 10 # Illegal, cannot start with number

Avoid Weird Symbols

1my@value = 20 # Illegal, '@' not allowed

Only underscores are permitted as symbols in names.

Names Too Short or Long

1x = 1 # Too short, not descriptive
2
3toolongvariablenameover253chars = 10 # Illegal, exceeds length limit

Cannot Use Python Reserved Words

1for = 5 # Illegal, 'for' is reserved word

When Name Mangling Happens

In Python, name mangling occurs when a name starts with two underscores. This changes it to _classname__variable to avoid conflicts with subclass names.

It’s best to avoid this double underscore naming to prevent confusion.

Conclusion

Here are some key points to remember about Python variable name legality:

• Follow snake_case conventions for names with underscores
• Avoid spaces, symbols besides underscores, and starting with numbers
• Do not use Python keywords or exceed the length limit
• Prioritize readable, descriptive names over abbreviations
• Use String_to_Uppercase and other tools to generate valid names
  String to Uppercase

  Effortlessly convert any text or string into uppercase format with our user-friendly online tool.

  Try Now

Adhering to Python’s naming rules and conventions prevents illegal variable names and unreadable code. Keep these guidelines in mind as you name variables in your Python programs.