[Python] ImportError: No module named 'matplotlib' -- Using Anaconda tensorflow environment

I'm just trying to learn Tensorflow, but am totally new to Python, so I'm using Anaconda I created a conda environment:

$ conda create −n tensorflow python =3.5


Of course I activated my conda environment

$ source activate tensorflow


Then I played a bit around in Spyder, tried to plot a MNIST-digit (copy-paste code from my tutor which is tested several times), it includes of course

import matplotlib.pyplot as plt
[...]
plt.plot(number)


but executing the Python file with bash gives me:

(tensorflow) leon@leon-linux:~/ANNsCourse/Session1$ python helloWorld.py
Traceback (most recent call last):
File "helloWorld.py", line 10, in <module>
import matplotlib.pyplot as plt
ImportError: No module named 'matplotlib'


I'm quite confused right now, as the (tensorflow) in the bash obviously denotes that my conda tensorflow environment works (at least from my understanding). Also, from what I understood, conda should have matplotlib built in, right? And it should also load this in my conda tensorflow environment, right? This is what my tutor's slide said

There is no need to install further packages like numpy or matplotlib, since Anaconda contains current versions of them already.'
​

and also what I was able to take from everything I Googled and StackOverflowed. Neither Googling nor StackOverflowing gave me any good answer (might also just be because I don't understand enough yet).

My best guess would be that I still have to include matplotlib into my tensorflow conda environment, but this would be contradicting both my tutor & Google, while I also would not know how to do this.

edit: conda list gave me that matplotlib was not in my tensorflowenvironment, so I went

conda install matplotlib


I'm still afraid something is wrong with my conda tensorflow environment, shouldn't the matplotlib have been in there by default? It also told me:

Package plan for installation in environment /home/leon/.conda/envs/tensorflow:

The following NEW packages will be INSTALLED:

cycler: 0.10.0-py35_0
dbus: 1.10.10-0
expat: 2.1.0-0
fontconfig: 2.12.1-3
freetype: 2.5.5-2
glib: 2.50.2-1
gst-plugins-base: 1.8.0-0
gstreamer: 1.8.0-0
icu: 54.1-0
jpeg: 9b-0
libffi: 3.2.1-1
libgcc: 5.2.0-0
libiconv: 1.14-0
libpng: 1.6.27-0
libxcb: 1.12-1
libxml2: 2.9.4-0
matplotlib: 2.0.0-np112py35_0
mkl: 2017.0.1-0
numpy: 1.12.0-py35_0
pcre: 8.39-1
pyparsing: 2.1.4-py35_0
pyqt: 5.6.0-py35_2
python-dateutil: 2.6.0-py35_0
pytz: 2016.10-py35_0
qt: 5.6.2-3
sip: 4.18-py35_0
six: 1.10.0-py35_0

Proceed ([y]/n)? y


Which tells me also numpy was missing? Can someone confirm this to be correct now, or is there something fishy with my conda?

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