Fix Python – Plot two histograms on single chart with matplotlib

I created a histogram plot using data from a file and no problem. Now I wanted to superpose data from another file in the same histogram, so I do something like this
n,bins,patchs = ax.hist(mydata1,100)
n,bins,patchs = ax.hist(mydata2,100)

but the problem is that for each interval, only the bar with the highest value appears, and the other is hid….