如何在Python中将嵌套列表映射到可迭代字典

Question

我有一个类列表及其先决条件存储在配对列表中:

classes = [
['Calculus', 'Geometry'],
['Trigonometry', 'Algebra'],
['Geometry', 'Trigonometry']
]

我想将这些类映射到特定的索引，以便为课程构建一个图表，使用如下内容:

course_index = {
0: 'Calculus'
1: 'Geometry' 
2: 'Trigonometry'
3: 'Algebra'
}

获取新的整型映射mapped_classes = [[0,1],[2,3],[1,2]]

为了创建course_index，我创建了一个空索引dict，并添加了classes中没有出现在course_index中的项目

course_index = {key: "" for key in range(4)}
index = 0
for x, y in classes:
if x not in course_index.values(): 
course_index[index] = x
index += 1
if y not in course_index.values(): 
course_index[index] = y
index += 1

我不明白的是如何将classes映射到相应的course_index来创建mapped_classes。

是否有一些映射函数可以简化这个过程?我试图解决这个问题如下，我无法改变当前类列表中的值。嵌套循环也非常低效。

for key, val in course_index: 
for x, y in classes:
if x = val: 
x = key
if y = val: 
y = key

Answer 1

翻转course_index字典。枚举类。

invert = {v: k for k, v in course_index.items()}
for i, row in enumerate(classes):
classes[i][0] = invert[classes[i][0]]
classes[i][1] = invert[classes[i][1]]
print(classes)

Answer 2

试试这样写:

mapped_classes = classes.copy()
for key, val in course_index.items():
for e, f in enumerate(classes):
for x in f:
if x == val:
mapped_classes[e][mapped_classes[e].index(x)] = key
print(mapped_classes)