I'm having a real hard time trying to learn Python 3 and right now I'm struggling with this one exercise.

I have to write a function that takes two arguments:

1) A string which is a DNA sequence.

2) A string of the same length as argument one (also a DNA sequence)

The function must return a float (the proportion of bases that are the same in two DNA sequences).

So, i know i have to write a function that will return something like this:

```
seq_similarity("ATGC","AGTT")

```

should return

```
0.75

```

I've only come this far and now I'm stuck even before I started:

```
def sequence_similarity(seq1,seq2):
    seq1="AGTC"
    seq2="AGTT"

```

Can you help me get started?