Displaying and editing sound in wave, python 2.7

I am trying to do the following using the module wave (and not another) in python 2.7:

• display the spectrum of a wav file


• add silences to a wav file at the beginning/end

Wave's documentation is rather shallow.

So far I have tried :

def display(filename):
    file=wave.open(filename,'r')
    freq=file._framerate
    n=file._nframes
    Y=file.readframes(n)
    plt.close()
    plt.plot(Y)
    plt.show()
    file.close()

but it would seem that file.readframes returns binary data, and I don't know how to use that.

For the part where I add silence, I have found some tutorials on how to create sound using wave, but I also need to replicate the old sound as follows :

def addSilence(filename,length);
    fileR=wave.open(filename,'r')
    fileW=wave.open('_'+filename,'w')

    # add silence here to fileW

    for i in fileR.readframes(fileR._nframes):
        #copy frames from fileR to fileW

    fileR.close()
    fileW.close()

How should I do it ?