Question

sentence = "The quick brown fox jumped over the lazy dog."
characters = {}

for character in sentence:
    characters[character] = characters.get(character, 0) + 1 

print(characters)

I don’t understand what characters.get(character, 0) + 1 is doing, rest all seems pretty straightforward.

Answer 1

The get method of a dict (like for example characters) works just like indexing the dict, except that, if the key is missing, instead of raising a KeyError it returns the default value (if you call .get with just one argument, the key, the default value is None).

So an equivalent Python function (where calling myget(d, k, v) is just like d.get(k, v) might be:

def myget(d, k, v=None):
  try: return d[k]
  except KeyError: return v

The sample code in your question is clearly trying to count the number of occurrences of each character: if it already has a count for a given character, get returns it (so it’s just incremented by one), else get returns 0 (so the incrementing correctly gives 1 at a character’s first occurrence in the string).