[Solved] mmdet install error: ERROR: Could not build wheels for pycocotools

x86_64-linux-gnu-gcc -pthread -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O2 -Wall -g -fstack-protector-strong -Wformat -Werror=format-security -g -fwrapv -O2 -fPIC -I/usr/local/lib/python3.8/dist-packages/numpy/core/include -I./common -I/usr/include/python3.8 -c pycocotools/_mask.c -o build/temp.linux-x86_64-3.8/pycocotools/_mask.o -Wno-cpp -Wno-unused-function -std=c99
      pycocotools/_mask.c:4:10: fatal error: Python.h: No such file or directory
       #include "Python.h"
                ^~~~~~~~~~
      compilation terminated.
      error: command '/usr/bin/x86_64-linux-gnu-gcc' failed with exit code 1
      [end of output]
  
  note: This error originates from a subprocess, and is likely not a problem with pip.
  ERROR: Failed building wheel for pycocotools
Failed to build pycocotools
ERROR: Could not build wheels for pycocotools, which is required to install pyproject.toml-based projects

The python version I use is 3.8 (replaced according to your version).

Solution:

Execute sudo apt install python3.8-dev

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