Python Invalid Character in Identifier(Beginner’s Guide)

As a Python programmer, you may have encountered the dreaded “SyntaxError: invalid character in identifier” error. This error can be perplexing, especially when you can’t seem to find the culprit character causing the issue. In this comprehensive blog post, we’ll dive deep into the root causes of this error, explore practical solutions, and provide code examples to help you understand and resolve it effectively.

What Causes the Invalid Character in Identifier Error?

The “SyntaxError: invalid character in identifier” error occurs when Python encounters a character that is not allowed in variable names, function names, or other identifiers. In Python, identifiers can only contain letters (both uppercase and lowercase), digits, and underscores. Any other character, such as spaces, punctuation marks, or special characters, is considered invalid and will trigger this error.

Here’s an example that illustrates the error:

value​s = 10  # Invalid character (ZERO WIDTH SPACE) in the identifier
print(value​s)

Output:

  File "example.py", line 1
    value​s = 10
         ^
SyntaxError: invalid character in identifier

In this case, the error is caused by the presence of a ZERO WIDTH SPACE character (\u200b) in the variable name value​s. Although this character is invisible to the naked eye, Python’s interpreter detects it and raises the error.

Common Causes of Invalid Characters in Identifiers

There are several common scenarios that can lead to the introduction of invalid characters in your code:

1. Copying and Pasting Code: When you copy code snippets from websites, PDF documents, or other formatted sources, invisible characters like ZERO WIDTH SPACES or curly quotes may be inadvertently included, causing this error.
2. Using Word Processors or Rich Text Editors: Word processors and rich text editors often introduce formatting characters or special symbols that can be problematic for Python code.
3. Non-English Keyboard Layouts: If you’re using a non-English keyboard layout, certain key combinations may produce characters that are not recognized by Python as valid identifiers.
4. Typos or Accidental Key Presses: Accidentally pressing a key combination that inserts an invalid character can also lead to this error.

Resolving the Invalid Character in Identifier Error

To resolve the “SyntaxError: invalid character in identifier” error, you need to identify and remove the offending character(s) from your code. Here are some effective strategies:

1. Retype the Problematic Line: One of the simplest solutions is to retype the line of code where the error is occurring. This ensures that no invisible characters are carried over from the previous version.
2. Use a Plain Text Editor: Avoid using word processors or rich text editors for writing Python code. Instead, use a dedicated plain text editor or an Integrated Development Environment (IDE) designed for programming.
3. Inspect the Code Carefully: Carefully inspect the line of code where the error is occurring, looking for any unusual or unexpected characters. You can also try printing the identifier as a string to reveal any hidden characters.

identifier = "value​s"
print(repr(identifier))  # Output: 'value\u200bs'

4. Use a Linter or Code Formatter: Linters and code formatters can help identify and fix issues like invalid characters in your code. Popular tools like pylint and black can be integrated into your development workflow.
5. Check Keyboard Settings: If you’re using a non-English keyboard layout, ensure that your keyboard settings are correct and that you’re not inadvertently inserting invalid characters.

Code Examples

Let’s explore some code examples to better understand the “SyntaxError: invalid character in identifier” error and how to resolve it.

Example 1: Copying and Pasting Code

# Copied code from a website
value​s = [1, 2, 3, 4, 5]
for value​ in value​s:
    print(value​)

Output:

  File "example.py", line 1
    value​s = [1, 2, 3, 4, 5]
         ^
SyntaxError: invalid character in identifier

In this example, the code was copied from a website, and invisible ZERO WIDTH SPACE characters (\u200b) were introduced into the variable names value​s and value​. To fix this, we can retype the code or use a plain text editor:

# Retyped code
values = [1, 2, 3, 4, 5]
for value in values:
    print(value)

Output:

1
2
3
4
5

Example 2: Using a Non-English Keyboard Layout

variablé = 10  # Accidental use of 'é' instead of 'e'
print(variablé)

Output:

  File "example.py", line 1
    variablé = 10
            ^
SyntaxError: invalid character in identifier

In this example, the variable name variablé contains an accidental ‘é’ character instead of ‘e’, likely due to a non-English keyboard layout. To fix this, we need to correct the variable name:

variable = 10
print(variable)

Output:

10

Example 3: Inspecting the Identifier

value​s = [1, 2, 3, 4, 5]
print(repr(value​s))  # Inspect the identifier

Output:

'value\u200bs'

In this example, we use the repr() function to inspect the identifier value​s. The output reveals the presence of the ZERO WIDTH SPACE character (\u200b), allowing us to identify and remove it from the code.