I have a checklist for Could not find a version that satisfies the requirement XYZ errors:
pip version check
What python version does the pip you're using refer to - is it the correct one? Imagine you have python3.4 and python3.5 installed and using pip3 command that is symlinked to pip3.4 while you assume it is symlinked to pip3.5. So issue first:
$ pip3 -V | grep -o "(.*)"
and verify the correct python version is printed. If it's not, then you have to find the correct pip executable: first check if you have version-specific commands available (e.g.
$ which pip3.6
for python3.6) and verify it is pointing to the correct python version with the command above (e.g. $ pip3.6 -V | grep -o "(.*)"). If there is no version-specific pip, start searching for the correct executable in the sys.prefix's bin subdirectory. Example on my machine:
$ python3.6 -c "import sys; print(sys.prefix)" | xargs -I {} find {}/bin -name pip*
/Library/Frameworks/Python.framework/Versions/3.6/bin/pip3.6
/Library/Frameworks/Python.framework/Versions/3.6/bin/pip3
platform check
You may have a platform mismatch on your target machine. Check what platform is recognized by pip:
$ python3.6 -c "import pip; print(pip.pep425tags.get_platform())"
For pip newer than 10.0:
$ python3.6 -c "import pip._internal as pip; print(pip.pep425tags.get_platform())"
The output should be macosx_10_11_x86_64 or newer (e.g. macosx_10_13_x86_64). If you have an older OSX, you will have to build TensorFlow from source because prebuilt packages exist for MacOS 10.11 and higher only.
Other platforms supported are: manylinux1_x86_64 (so all the 64bit Linux distros with glibc>2.5 should do just fine, no 32bit distros or some exotic ones like Alpine with musl) and win_amd64 (64bit Windows).
ABI check
A less common problem is the ABI mismatch: you can check your platform's ABI with
$ python3.6 -c "import pip; print(pip.pep425tags.get_abi_tag())"
For pip newer than 10.0:
$ python3.6 -c "import pip._internal as pip; print(pip.pep425tags.get_abi_tag())"
The supported ABI tags are currently: cp27m, cp27mu, cp33m, cp34m, cp35m, cp36m. The above command should print you one of the tags listed. If not, you will have to build/install from sources.
Last notes
A rare case could be a misconfigured PyPI index: run
$ pip3 install --upgrade tensorflow --verbose
Collecting tensorflow
2 location(s) to search for versions of tensorflow:
* https://pypi.python.org/simple/tensorflow/
* https://my.pypi.server/base/dev/+simple/tensorflow/
...
Check if https://pypi.python.org/simple/tensorflow/ is in the list. If not, try the command
$ pip3 install --upgrade tensorflow --index-url=https://pypi.python.org/simple
If the installation succeeds, check if you have PIP_INDEX_URL environment variable set and clear it. If not, check if you have the file ~/.pip/pip.conf present and if it has index-url entry defined.
