I tried all combinations and nothing made import geohash work:

pip install geohash
pip3 install geohash
apt-get install python-dev
pip3 install python-geohash

the 4th one isn't even installing but threw an error on me saying:
src/geohash.cpp:538:20: fatal error: Python.h: No such file or directory
   #include 
                      ^
  compilation terminated.
  error: command 'x86_64-linux-gnu-gcc' failed with exit status 1
Thanks @William D. Irons. The issue got fixed when I did sudo apt-get install libpython3.7-dev
error: command 'x86_64-linux-gnu-gcc' failed with exit status 1 while doing pip3 install python-geohash