This is a handy error most people face while starts developing in python environment. Make sure you try several ways before smiling-
If you are using python3 (people started to forget about python2 already) try-
pip3 install Flask
You can also specify the version of Flask by
pip3 install Flask==0.13.2
→ Another reason could be the python file name which doesn’t mean to be ‘flask’ anyway which matches flask library file name. If that is the case-
*** Renaming the ‘flask.py’ to ‘somethingelse.py’ may help.