Question

这是我教科书中的GPA计算器代码。我想问一些我不明白的事情。

# Semester GPA Calculation

def convertGrade(grade):
    if grade == 'A+':
        return 4
    if grade == 'A':
        return 3.7
    if grade == 'A-':
        return 3.3
    if grade == 'B+':
        return 3.0
    if grade == 'B':
        return 2.7
    if grade == 'B-':
        return 2.3
    if grade == 'C+':
        return 2.0
    if grade == 'C':
        return 1.7
    if grade == 'C-':
        return 1.3
    if grade == 'D+':
        return 1.0
    if grade == 'D':
        return 0.7
    if grade == 'D-':
        return 0.3
    else:
        return 0


def getGrades():
semester_info = []
more_grades = True
empty_str = ''

    while more_grades:
        course_grade = input('Enter grade (hit Enter if done): ')
        while course_grade not in ['A+', 'A', 'A-', 'B+', 'B', 'B-', 'C+', 'C', 'C-', 'D+', 'D', 'D-', 'E+', 'E', 'E-', 'F', empty_str]:
        course_grade = input('Enter letter grade you received: ')
     if course_grade == empty_str:
            more_grades = False
     else:
         num_credits = int(input('Enter number of credits: '))
         semester_info.append([num_credits, course_grade])

 return semester_info

def calculateGPA(sem_grades_info, cumm_gpa_info):
    sem_quality_pts = 0
    sem_credits = 0
    current_cumm_gpa, total_credits = cumm_gpa_info

    for k in range(len(sem_grades_info)):
        num_credits, letter_grade = sem_grades_info[k]

        sem_quality_pts = sem_quality_pts + \
                      num_credits * convertGrade(letter_grade)

        sem_credits = sem_credits + num_credits


    sem_gpa = sem_quality_pts / sem_credits
    new_cumm_gpa = (current_cumm_gpa * total_credits + sem_gpa * \
                sem_credits) / (total_credits + sem_credits)

    return (sem_gpa, new_cumm_gpa)

# ---- main

# program greeting
print('This program calculates new semester and cumulative GPAs\n')

# get current GPA info
total_credits = int(input('Enter total number of earned credits: '))
cumm_gpa = float(input('Enter your current cummulative GPA: '))
cumm_gpa_info = (cumm_gpa, total_credits)

# get current semester grade info
print()
semester_grades = getGrades()

# calculate semester gpa and new cumulative gpa
semester_gpa, cumm_gpa = calculateGPA(semester_grades, cumm_gpa_info)

#display semester gpa and new cummulative gpa
print('\nYour semester GPA is', format(semester_gpa, '.2f'))
print('Your new cummulative GPA is', format(cumm_gpa, '.2f'))

current_cumm_gpa, total_credits = cumm_gpa_info下面的含义是什么？它会创建一个新阵列吗？我试过更简单，但它不起作用。

  def calculateGPA(sem_grades_info, cumm_gpa_info):
      sem_quality_pts = 0
      sem_credits = 0
      current_cumm_gpa, total_credits = cumm_gpa_info

Answer 1

从这一行：

cumm_gpa_info = (cumm_gpa, total_credits)

我们可以看到cumm_gpa_info是两个值的a tuple。然后current_cumm_gpa, total_credits = cumm_gpa_info 将元组中的值解包为两个变量，第一个变为current_cumm_gpa，第二变为total_credits。这是一种更简单的做法：

current_cumm_gpa = cumm_gpa_info[0]
total_credits = cumm_gpa_info[1]

来自文档：

这足够恰当地称为序列解包并且适用于右侧的任何序列。序列拆包需要这样做在等号的左侧有多少变量序列中有元素。请注意，多个赋值是实际上只是元组打包和序列解包的组合。

Answer 2

跟踪您的计划，我们会看到以下内容：

>>> total_credits = int(input('Enter total number of earned credits: '))
    #3.2
>>> cumm_gpa = float(input('Enter your current cummulative GPA: '))
    #4.6
>>> cumm_gpa_info = (cumm_gpa, total_credits)

>>> cumm_gpa_info
    (3.2 , 4.6)

>>> type(cumm_gpa_info)
    Tuple

因此，我们发现cumm_gpa_info是Tuple。现在将其传递给函数。

>>> ... = calculateGPA(semester_grades, cumm_gpa_info)

#inside function
>>> current_cumm_gpa, total_credits = cumm_gpa_info
#current_cumm_gpa, total_credits = (3.2 , 4.6)

>>> current_cumm_gpa
    3.2
>>> total_credits
    4.6

我们可以看到，unpacked中的值为tuple，并分配给current_cumm_gpa＆amp;分别为total_credits。

类似于：

>>> current_cumm_gpa = cumm_gpa_info[0]
>>> total_credits = cumm_gpa_info[1]

注意：抱歉，如果它不完全是在控制台上看起来的样子。无法访问我的电脑，现在就把它写在我的手机上。所以大概看看它的样子。

python，GPA计算器，关于工作代码

2 个答案: