Invalid Syntax Python

By | September 27, 2021
Invalid Syntax python

Python has a neat and simple syntax, but it does not guarantee that you wouldn’t commit any syntax error. 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 distinct as compared to other programming languages. If you are entirely new to Python, then there is a high chance that you will be commenting some Syntax Error. So for a developer, it is very important to know how to read and debug syntax error if the code contains any.

In this tutorial, we have provided a brief description of Python SyntaxError and how can we debug it?

Invalid Python Syntax

When we run our Python source code, the Python interpreter parses the code line by line and simultaneously execute 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.

The SyntaxError generally occur when we use such formatting or write such code which does not satisfy the Python coding rules.

<Note> Apart from the SyntaxError there are many other errors in Python. In this tutorial, we have only covered the SyntaxError.

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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.

Example

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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 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 the specify the type of 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 the brief idea 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.

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 at the left side of the operator and value on the right side. If we do not follow this syntax, then the interpreter throws a SyntaxError.

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 at the right of the Assignment operator.
  • In the second and third examples, we tried to assign a value to another value which also causes a SyntaxError.

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.

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

Missing brackets quotes, and parentheses

However, unlike other programming languages, we do not use brackets to represent a function definition or body; 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 object, we need to make sure that brace has 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 other for closing, it needs to be same.

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 '['

Invalid Dictionary Syntax

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

Example

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

Conclusion

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. IDE also helps in reducing the SyntaxErrors. In IDEs, we get some built-in features which eliminate some of the common SyntaxError by provides live text highlight if we write the wrong syntax.

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Author: Vinay

I am a Full Stack Developer with a Bachelor's Degree in Computer Science, who also loves to write technical articles that can help fellow developers.

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