Pip install error ModuleNotFoundError: No module named 'pystan'

pip --version
pip 9.0.1 from /Users/miasool/pyenvs/xor_ai/lib/python3.6/site-packages (python 3.6)

pip install fbprophet
Collecting fbprophet
  Downloading fbprophet-0.2.1.tar.gz
Requirement already satisfied: matplotlib in /Users/miasool/pyenvs/xor_ai/lib/python3.6/site-packages (from fbprophet)
Requirement already satisfied: pandas>=0.18.1 in /Users/miasool/pyenvs/xor_ai/lib/python3.6/site-packages (from fbprophet)
Collecting pystan>=2.14 (from fbprophet)
  Downloading pystan-2.17.0.0-cp36-cp36m-macosx_10_6_intel.macosx_10_9_intel.macosx_10_9_x86_64.macosx_10_10_intel.macosx_10_10_x86_64.whl (35.2MB)
    100% |████████████████████████████████| 35.2MB 43kB/s
Requirement already satisfied: python-dateutil>=2.0 in /Users/miasool/pyenvs/xor_ai/lib/python3.6/site-packages (from matplotlib->fbprophet)
Requirement already satisfied: pyparsing!=2.0.4,!=2.1.2,!=2.1.6,>=2.0.1 in /Users/miasool/pyenvs/xor_ai/lib/python3.6/site-packages (from matplotlib->fbprophet)
Requirement already satisfied: cycler>=0.10 in /Users/miasool/pyenvs/xor_ai/lib/python3.6/site-packages (from matplotlib->fbprophet)
Requirement already satisfied: numpy>=1.7.1 in /Users/miasool/pyenvs/xor_ai/lib/python3.6/site-packages (from matplotlib->fbprophet)
Requirement already satisfied: six>=1.10 in /Users/miasool/pyenvs/xor_ai/lib/python3.6/site-packages (from matplotlib->fbprophet)
Requirement already satisfied: pytz in /Users/miasool/pyenvs/xor_ai/lib/python3.6/site-packages (from matplotlib->fbprophet)
Collecting Cython!=0.25.1,>=0.22 (from pystan>=2.14->fbprophet)
  Downloading Cython-0.27.3-cp36-cp36m-macosx_10_6_intel.macosx_10_9_intel.macosx_10_9_x86_64.macosx_10_10_intel.macosx_10_10_x86_64.whl (4.7MB)
    100% |████████████████████████████████| 4.7MB 290kB/s
Building wheels for collected packages: fbprophet
  Running setup.py bdist_wheel for fbprophet ... error
  Complete output from command /Users/miasool/pyenvs/xor_ai/bin/python3.6 -u -c "import setuptools, tokenize;__file__='/private/var/folders/c0/mz0pnjn131d5rsl43kr5my6xh2lw2t/T/pip-build-19fj5puw/fbprophet/setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" bdist_wheel -d /var/folders/c0/mz0pnjn131d5rsl43kr5my6xh2lw2t/T/tmpe7pukz0npip-wheel- --python-tag cp36:
  running bdist_wheel
  running build
  running build_py
  creating build
  creating build/lib
  creating build/lib/fbprophet
  creating build/lib/fbprophet/stan_models
  Traceback (most recent call last):
    File "<string>", line 1, in <module>
    File "/private/var/folders/c0/mz0pnjn131d5rsl43kr5my6xh2lw2t/T/pip-build-19fj5puw/fbprophet/setup.py", line 126, in <module>
      """
    File "/Users/miasool/pyenvs/xor_ai/lib/python3.6/site-packages/setuptools/__init__.py", line 129, in setup
      return distutils.core.setup(**attrs)
    File "/usr/local/Cellar/python3/3.6.2/Frameworks/Python.framework/Versions/3.6/lib/python3.6/distutils/core.py", line 148, in setup
      dist.run_commands()
    File "/usr/local/Cellar/python3/3.6.2/Frameworks/Python.framework/Versions/3.6/lib/python3.6/distutils/dist.py", line 955, in run_commands
      self.run_command(cmd)
    File "/usr/local/Cellar/python3/3.6.2/Frameworks/Python.framework/Versions/3.6/lib/python3.6/distutils/dist.py", line 974, in run_command
      cmd_obj.run()
    File "/Users/miasool/pyenvs/xor_ai/lib/python3.6/site-packages/wheel/bdist_wheel.py", line 204, in run
      self.run_command('build')
    File "/usr/local/Cellar/python3/3.6.2/Frameworks/Python.framework/Versions/3.6/lib/python3.6/distutils/cmd.py", line 313, in run_command
      self.distribution.run_command(command)
    File "/usr/local/Cellar/python3/3.6.2/Frameworks/Python.framework/Versions/3.6/lib/python3.6/distutils/dist.py", line 974, in run_command
      cmd_obj.run()
    File "/usr/local/Cellar/python3/3.6.2/Frameworks/Python.framework/Versions/3.6/lib/python3.6/distutils/command/build.py", line 135, in run
      self.run_command(cmd_name)
    File "/usr/local/Cellar/python3/3.6.2/Frameworks/Python.framework/Versions/3.6/lib/python3.6/distutils/cmd.py", line 313, in run_command
      self.distribution.run_command(command)
    File "/usr/local/Cellar/python3/3.6.2/Frameworks/Python.framework/Versions/3.6/lib/python3.6/distutils/dist.py", line 974, in run_command
      cmd_obj.run()
    File "/private/var/folders/c0/mz0pnjn131d5rsl43kr5my6xh2lw2t/T/pip-build-19fj5puw/fbprophet/setup.py", line 46, in run
      build_stan_models(target_dir)
    File "/private/var/folders/c0/mz0pnjn131d5rsl43kr5my6xh2lw2t/T/pip-build-19fj5puw/fbprophet/setup.py", line 28, in build_stan_models
      from pystan import StanModel
  ModuleNotFoundError: No module named 'pystan'

  ----------------------------------------
  Failed building wheel for fbprophet
  Running setup.py clean for fbprophet
Failed to build fbprophet
Installing collected packages: Cython, pystan, fbprophet
  Running setup.py install for fbprophet ... done
Successfully installed Cython-0.27.3 fbprophet-0.2.1 pystan-2.17.0.0

However with the second run it showed no error

pip install fbprophet
Requirement already satisfied: fbprophet in /Users/miasool/pyenvs/xor_ai/lib/python3.6/site-packages
Requirement already satisfied: matplotlib in /Users/miasool/pyenvs/xor_ai/lib/python3.6/site-packages (from fbprophet)
Requirement already satisfied: pandas>=0.18.1 in /Users/miasool/pyenvs/xor_ai/lib/python3.6/site-packages (from fbprophet)
Requirement already satisfied: pystan>=2.14 in /Users/miasool/pyenvs/xor_ai/lib/python3.6/site-packages (from fbprophet)
Requirement already satisfied: pyparsing!=2.0.4,!=2.1.2,!=2.1.6,>=2.0.1 in /Users/miasool/pyenvs/xor_ai/lib/python3.6/site-packages (from matplotlib->fbprophet)
Requirement already satisfied: numpy>=1.7.1 in /Users/miasool/pyenvs/xor_ai/lib/python3.6/site-packages (from matplotlib->fbprophet)
Requirement already satisfied: six>=1.10 in /Users/miasool/pyenvs/xor_ai/lib/python3.6/site-packages (from matplotlib->fbprophet)
Requirement already satisfied: cycler>=0.10 in /Users/miasool/pyenvs/xor_ai/lib/python3.6/site-packages (from matplotlib->fbprophet)
Requirement already satisfied: pytz in /Users/miasool/pyenvs/xor_ai/lib/python3.6/site-packages (from matplotlib->fbprophet)
Requirement already satisfied: python-dateutil>=2.0 in /Users/miasool/pyenvs/xor_ai/lib/python3.6/site-packages (from matplotlib->fbprophet)
Requirement already satisfied: Cython!=0.25.1,>=0.22 in /Users/miasool/pyenvs/xor_ai/lib/python3.6/site-packages (from pystan>=2.14->fbprophet)

[johnnyheineken]

I had this issue with Python 3.9, miniconda debian docker image

If you are currently having issues with importing pystan in fbprophet, this is most likely caused by pystan 3.0.
See here:

Use import stan instead of import pystan.

I recommend to downgrade pystan to 2.19.1.1 - latest pre-3 version. I recommend to downgrade to python 3.8 (repositories contain pre-compiled binaries, but not for 3.9)

Installation worked for me to install pystan using conda, and fbprophet using pip

If you would like to use 3.9 - check that g++, gcc is installed.

[z4yed]

According to the installation page of FbProphet:

Install pystan with pip before using pip to install prophet

pystan>=3.0 is currently not supported

$ pip install pystan==2.19.1.1 $ $ pip install prophet