Python - finding INDELS and SNPS

seq_a = 'GAGAGATTTTCCAATTCGACG-------CGGGGTCAGG--GAAATTT'
  
seq_b = 'GAGAGATTGGCCTTAACTACCCAACCCACGGCCTGACCGAGGTCTTC'

G
A
C
T
= Bases

-
= INDEL

PYTHON - I am very new to programming and need some help, I would like to write a python program that will first find indels '-' in seq_a and then compare both sequences (seq_a and seq_b) downstream and upstream from the the indels counting the number of differences between the bases. 

e.g. 
seq_a - GG--GAAA
seq_b - CCGAGGTC

this example has 5 SNPS upstream and downstream from the the indel c-g, c-g, a-g, a-t, a-c

I was wondering if anyone could give me any pointers or ideas how I would start of this program?

thanks :)