Can I show an index number when raising a ValueError?-CodePudding

I want to check the input format for a given function with a list of lists as input. I have used the code below to indicate at which index the input file has the wrong format:

for i, doc in enumerate(input_file):
    if not isinstance(doc,list):
        raise ValueError("The element of input_file at index '   str(i)   ' is not a list")

However, the output of this code (with wrong input) is:

ValueError: The element of input_file at index '   str(i)   ' is not a list

So, it does not convert str(i) to an actual number. Is it possible to get a number there?

CodePudding user response：

Use double (") instead of single quotes (')

CodePudding user response：

The syntax was wrong. You have not concatenated the numbers. The code raise ValueError("The element of input_file at index ' str(i) ' is not a list") basically considers ' str(i) ' as a string only.

Try this:

raise ValueError(f"The element of input_file at index '{i}' is not a list")