Printing a pattern through the use of a dictionary
For how you're using it, it seems like a list of lists would make more sense than a dict. This is somewhat like a 2-dimensional array in C.

Your mtn initialization becomes:

mtn = []


You'll need to do a little more work in space_mtn to generate the sublists:

def space_mtn(height,mtn):
    for i in range(height):
        mtn.append([])             # Append an empty sublist at each level
        for j in range(2*height+2):
            mtn[-1].append(" ")    # Append a space to the end of the currently-last list
    return


Now in hash_mtn and print_mtn, just change your mtn[i,j] calls to mtn[i][j].

Now, there are lots of ways to make this code less C-like and more "Pythonic". Such discussions are probably better for Code Review. I'll just say that it's possible (although not necessarily "best") to get equivalent functionality by replacing everything after your input while loop with one line:

print('\n'.join('{0:&gt;{1}}  {0:{1}}'.format('#'*(i+1), height) for i in range(height)))