Python IndentationError unindent does not match any outer indentation level

I had the same problem quite a few times. It happened especially when i tried to paste a few lines of code from an editor online, the spaces are not registered properly as 'tabs' or 'spaces'.

However the fix was quite simple. I just had to remove the spacing across all the lines of code in that specific set and space it again with the tabs correctly. This fixed my problem.

You have mixed indentation formatting (spaces and tabs)

On Notepad++

Change Tab Settings to 4 spaces

Go to Settings -> Preferences -> Tab Settings -> Replace by spaces

Fix the current file mixed indentations

Select everything CTRL+A

Click TAB once, to add an indentation everywhere

Run SHIFT + TAB to remove the extra indentation, it will replace all TAB characters to 4 spaces.

You are mixing tabs and spaces. Don't do that. Specifically, the __init__ function body is indented with tabs while your on_data method is not.

Here is a screenshot of your code in my text editor; I set the tab stop to 8 spaces (which is what Python uses) and selected the text, which causes the editor to display tabs with continuous horizontal lines:

You have your editor set to expanding tabs to every fourth column instead, so the methods appear to line up.

Run your code with:

python -tt scriptname.py

and fix all errors that finds. Then configure your editor to use spaces only for indentation; a good editor will insert 4 spaces every time you use the TAB key.