Invalid Syntax Python: What is Invalid Python SyntaxError?

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Invalid Syntax Python: What is Invalid Python SyntaxError?
vinaykhatri

Vinay Khatri
Last updated on May 30, 2024

    Python has a neat and simple syntax, but it does not guarantee that you wouldn't commit any syntax error. Invalid syntax Python is a common issue among newcomers and experienced developers. Developers who are learning Python for the first time or just have moved to Python from a different programming language may find Python a little bit different as compared to other programming languages.

    If you are entirely new to Python, then there is a high chance that you will be commenting on some syntax error. So for a developer, it is very important to know how to read and debug syntax errorsp if the code contains any. In this tutorial, we have provided a brief description of Python SyntaxError and how to debug it.

    Invalid Python Syntax

    When we run our Python source code, the Python interpreter parses the code line by line and simultaneously executes it, and this parsing and execution of code come useful in code debugging. The Python interpreter stops executing the code when it encounters any semantic or syntax error. SyntaxError generally occurs when we use formatting or write code that does not satisfy the Python coding rules.

    <Note>

    Other than the SyntaxError, there are many other errors in Python. In this tutorial, we have only covered the SyntaxError.

    Python SyntaxError and Trackback

    If there is a syntax error in a Python program, then the interpreter throws a SyntaxError with a trackback that provides valuable information about the error. The Trackback information generally contains the code line number where the error occurred and some other information.

    Code Example

    a = {1:"one", 2:"two" 3:"three"}
    
    print(a)

    Output

    File example.py, line 1
    
        a = {1:"one", 2:"two" 3:"three"}
    
                              ^
    
    SyntaxError: invalid syntax

    Here in this example, we did not pass the comma between "two" 3. That's why the interpreter throws an error. Here you can see that the trackback locates the error line, and ^ (the carrot symbol) points to the error location.

    Trackback Information

    The trackback generally displays the following information.

    • File name of the source code.
    • Error line number of the code.
    • Caret symbol (^) to locate the exact error location.
    • Error message specifies the type of the error.

    <Note> With Python custom error, we can specify our own error messages.

    Common Syntax Errors

    When the Python interpreter throws the SyntaxError, using the trackback information, we get a brief idea of where the error code is present and what might be the error. Here we have provided some of the common SyntaxErrors you may face while executing the Python code.

    1) Invalid use of Assignment Operator (=)

    The assignment operator is generally used to assign values to a variable. When we use the assignment operator, the variable or identifier should be on the left side of the operator and the value on the right side. If we do not follow this syntax, then the interpreter throws a SyntaxError.

    Code Example:

    >>> 4 = a
    
    File "<stdin>", line 1
    
    SyntaxError: cannot assign to literal
    
    >>> 4 = 3
    
    File "<stdin>", line 1
    
    SyntaxError: cannot assign to literal
    
    >>> "a" = 4
    
    File "<stdin>", line 1
    
    SyntaxError: cannot assign to literal
    • In the first example, the SyntaxError occurred because the value 4 is at the left side, and identifier a is at the right side of the assignment operator.
    • In the second and third examples, we tried to assign a value to another value that also causes a SyntaxError.

    2) Writing and using the wrong Python keyword

    In Python, we have some reserved characters that can not be used as identifiers or variables. Some of the keywords work alone, and some work with proper syntax. If we misspell any keyword that works with a syntax then we will receive the SyntaxError.

    Code Example:

    #Using a keyword as an identifier 
    
    >>> for = 1
    
      File "<stdin>", line 1
    
        for = 1
    
            ^
    
    SyntaxError: invalid syntax
    
    #Misspelling a keyword
    
    >>> fro i in range(10):
    
      File "<stdin>", line 1
    
        fro i in range(10):
    
            ^
    
    SyntaxError: invalid syntax

    3) Missing brackets, quotes, and parentheses

    However, unlike other programming languages, we do not use brackets to represent a function definition or body in Python. Still, we use braces and parenthesis to group tuples, enclose function parameters, and arithmetic operations. If we use braces to represent a tuple or any other Python object, we need to make sure that braces have a valid opening and ending. This valid opening and closing concept also apply to quotes. In Python, we can use single and double quotes to represent a string. We can not use one quotation for string opening and the other for closing. It needs to be the same.

    Code Examples:

    >>> string ="hello'
    
      File "<stdin>", line 1
    
        string ="hello'
    
                      ^
    
    SyntaxError: EOL while scanning string literal 
    
    #no closing quote:
    
    >>> string ="hello
    
      File "<stdin>", line 1
    
        string ="hello
    
                     ^
    
    SyntaxError: EOL while scanning string literal
    
    #no ending brackets
    
    >>> count = {1: "one", 2:"two"}
    
    >>> print(count["1" )
    
      File "<stdin>", line 1
    
    SyntaxError: closing parenthesis ')' 
    
                 does not match opening parenthesis '['

    4) Invalid Dictionary Syntax

    Often, beginners commit mistakes with Python dictionaries. A dictionary is a collection of keys and values. In a Python dictionary , we use a colon (:) to bind a key with its values.

    Code Example:

    >>> count = {1 = "one", 2:"two"}
    
      File "<stdin>", line 1
    
       count = {1 = "one", 2:"two"}
    
                  ^
    
       SyntaxError: invalid syntax

    Conclusion

    The invalid syntax is a common issue in Python. SyntaxError is one of the most common errors we can encounter while writing Python code. Trackback information is not often accurate, so we need to improve our error detecting and debugging skills. IDEs also help in reducing invalid syntax errors. In IDEs, we get some built-in features that eliminate some of the common SyntaxError by providing live text highlighting if we write the wrong syntax.

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