TeXShop can't find "required tool" pdflatex

When I attempt to typeset LaTeX I get the dialogue box pop up "Can’t find required tool" and I copy and paste here the rest: "/Library/TeX/texbin
/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/tests/baseline_images/test_backend_pgf/pgf_pdflatex.pdf
/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/tests/baseline_images/test_backend_pgf/pdflatex does not exist. TeXShop is a front end for TeX, but you also need a TeX distribution. Perhaps such a distribution was not installed or was removed during a system upgrade. If so, go to http://tug.org/mactex and follow the instructions to install MacTeX or BasicTeX."

Running pdflatexmk I get the following in the console:

Latexmk: This is Latexmk, John Collins, 18 June 2019, version: 4.65.
Rule 'pdflatex': File changes, etc:
   Changed files, or newly in use since previous run(s):
      'QFT.tex'
------------
Run number 1 of rule 'pdflatex'
------------
------------
Running 'pdflatex  --synctex=1 --file-line-error  -recorder  "QFT.tex"'
------------
Latexmk: applying rule 'pdflatex'...
sh: pdflatex: command not found
Latexmk: fls file doesn't appear to have been made.
Collected error summary (may duplicate other messages):
  pdflatex: Command for 'pdflatex' gave return code 127
      Refer to 'QFT.log' for details
----------------------
This message may duplicate earlier message.
Latexmk: Failure in processing file 'QFT.tex':
   (Pdf)LaTeX didn't generate the expected log file 'QFT.log'
----------------------
Latexmk: Use the -f option to force complete processing,
 unless error was exceeding maximum runs, or warnings treated as errors.
Latexmk: Errors, so I did not complete making targets

I have tried uninstalling TeXShop (deleting all related files too) and reinstalling, but I always get the same error. It seems to me that it is trying to find pdflatex in a strange location involving a file from another program – This "python.framework" thing, but I haven’t told it to do so. In fact, in the preferences menu, under "engine", the path it is being told to follow to find pdflatex is the default one – /Library/Tex/bin. I can find no references to this Python file in any of the settings available to me to change it.

I can see a lot of people have had similar issues, but people always say to uninstall and reinstall, but this hasn’t worked for me (I’ve done it 3 times) and I have also tried the other most popular solutions, but to no avail. I have also tried BasicTex, but this program didn’t seem to run properly for me (I think unrelated to this problem, though).

I am running macOS Catalina, if this is needed.