Guido invented Python to save us all from this kind of unreadable code. 
The first line and last line produce completely different lists; not the same packages.
So although you may intend to use pip list --outdated, you actually don’t.
The second line removes the first line’s list from the text file, so you never see it.
Check this again: ([HowTo] Upgrade many python packages with pip)
Seems like you need to slow down, and learn a subject thoroughly before you try to use it.
The crazy shell stuff works, but you need only awk -F "==" '{print $1}', as in
pip freeze | awk -F "==" '{print $1}' > textfile
to remove version numbers.