python - 试图得到总和，但似乎没有用

Question

我正在学习 python 并且正在研究这个问题，但似乎无法让它发挥作用。执行此代码时，我在不同的行上得到数字 1 到 8。我怎样才能只打印 8 的计数？

honor_roll_count = 0
student_grades = ["A", "C", "B", "B", "C", "A", "F", "B", "B", "B", "C", "A"]
for grade in student_grades:
    if grade in "AB":
        honor_roll_count = honor_roll_count + 1
        print honor_roll_count

Answer 1

你print是缩进的，这意味着它if在循环内部for，所以它发生在每个“A”或“B”上。你想要它在循环之后。

for grade in student_grades:
    if grade in "AB":
        honor_roll_count = honor_roll_count + 1
print honor_roll_count

Answer 2

将print语句向左移动，两个缩进级别：

for grade in student_grades:
    if grade in "AB":
        honor_roll_count = honor_roll_count + 1
print honor_roll_count

现在它将在循环完成后执行，而不是循环的每次迭代。

Answer 3

honor_roll_count = 0
student_grades = ["A", "C", "B", "B", "C", "A", "F", "B", "B", "B", "C", "A"]
for grade in student_grades:
    if grade in "AB":
        honor_roll_count += 1
print honor_roll_count

Answer 4

honor_count = student_grades.count("A") + student_grades.count("B")

或者

honor_count = sum([student_grades.count(grade) for grade in "AB"])