How to use requirements.txt to install all dependencies in a python project

If you are using Linux OS:

1. Remove matplotlib==1.3.1 from requirements.txt
2. Try to install with sudo apt-get install python-matplotlib
3. Run pip install -r requirements.txt (Python 2), or pip3 install -r requirements.txt (Python 3)
4. pip freeze > requirements.txt

If you are using Windows OS:

1. python -m pip install -U pip setuptools
2. python -m pip install matplotlib

pip install -r requirements.txt for python 2.x

pip3 install -r requirements.txt for python 3.x (in case multiple versions are installed)