TypeError: cannot concatenate object of type '<class 'int'>'; only Series and DataFrame objs are valid

This error occurs when you try to concatenate an object of type 'int' with another object using the '+' operator. However, the '+' operator is only defined for concatenating Series and DataFrame objects in pandas.

For example, if you have two Series objects s1 and s2, you can concatenate them using the '+' operator like this:

s3 = s1 + s2

But if you try to concatenate an integer with a Series object, you will get the TypeError:

s3 = s1 + 5  # raises TypeError

To fix this error, make sure that you are only concatenating Series and DataFrame objects using the '+' operator. If you need to concatenate an integer with a Series object, you can convert the integer to a Series object first:

s3 = s1 + pd.Series([5])