What does it mean the last line?

Question

Hello

If it is not too much trouble, can someone explain to me in a general way what each line of this code means ?, but specifically the last one

def count_char(text, char):
count = 0
for c in text:
if c == char:
count += 1
return count

filename = input("Enter a filename: ")
with open(filename) as f:
text = f.read()

for char in "abcdefghijklmnopqrstuvwxyz":
perc = 100 * count_char(text, char) / len(text)
print("{0} - {1}%".format(char, round(perc, 2)))

Answer 1

That's a string formatting.

{0} and {1} will be replaced against arguments 1 and 2 in the parentheses.

First argument is char, the second the value perc, rounded to two decimal places.