At some point in your research career you may be asked for your matplotlib plots to use Helvetica.
The following code may work for you:
import matplotlib
matplotlib.rcParams['font.family'] = 'sans-serif'
matplotlib.rcParams['font.sans-serif'] = 'Helvetica'
If it doesnt try this package.
To install:
pip install -e git+https://github.com/amcpherson/vetica.git#egg=vetica
To have matplotlib use Helvetica for fonts:
import vetica.mpl