Answer:
sen = input("Enter a sentence: ")
sen = sen.lower()
sen = sen.replace(" ","")
sen = list(sen)
sen.sort()
print(sen)
sen1 = []
for i in sen:
if i not in sen1:
sen1.append(i)
print(sen1)
sen2 = []
for i in sen1:
sen2.append(sen.count(i))
print(sen2)
for i in range(len(sen1)):
print("The letter",sen1[i],"appears",sen2[i],"times")