How I can count letter in sentence in Python

Please help in writing a program that will count the letters ‘a’ in a sentence. I need to use a ‘for’ loop.

text = input("Give a sentence and I will count the number of letters 'a'\n") 
for letter in text:
    a_text = text.count('a')
    print(a_text)

>Solution :

text = input("Give a sentence and I will count the number of letters 'a'\n")

count = 0
for letter in text:
    if letter == 'a':
        count += 1

print("The number of 'a' is:", count)