Detecting and removing interferences from a signal
I'd recommend using a median filter to smooth your signal. A median filter will get rid of the outliers, or the spikes in your signal. The length of the median filter will have to be determined by how frequently the spikes appear in your signal. The median filter is available in Python as numpy.median.
If you want to retrieve the spikes (the interference signal), you can simply subtract the filtered signal from the noisy signal to get the interference.