os.walk gives you the path and filename. you can then use
stats = os.stat(path+name)
stats.st_size
to get the file size in bytes. so you could just change up your current function to something like:
def find_by_size(size, path):
result = []
for root, dirs, files in os.walk(path):
if os.stat(path+name).st_size == size:
result.append((os.path.join(name), stats.st_size))
else:
print ("Nothing of size %d was found" % size)
return result
also you don't need to pass result in, since you're just replacing it with an empty list. Python can return lists from a function.