第二次迭代不起作用

Question

我不得不回答的问题是：

Implement a function with signature

def expand_one_or(course_lists): 

This function takes a list of lists of strings course_lists, and modifies it as follows:

• It finds the first list (call it lis) in course_lists in which "/" occurs.

• It then finds the coordinate of the first "/" in lis (say i).

• If lis[i-1] and lis[i+1] exist and are both courses, lis is replaced in course_lists with two new lists: a list identical to lis but with lis[i] and lis[i+1] removed, and a list identical to lis but with lis[i] and lis[i-1] removed.

• Otherwise, all that happens is that lis[i] is removed from lis.

For example, if course_lists is:

[ ["CSC148H1", "/", "CSC150H1", ",", "CSC165H1", "/", "CSC240H1", "/", 
"CSC148H1", ";", "/"] ] 

expand_one_or finds the first "/", and modifies course_lists to become

[ ["CSC148H1", ",", "CSC165H1", "/", "CSC240H1", "/", "CSC148H1", ";", "/"], 
["CSC150H1", ",", "CSC165H1", "/", "CSC240H1", "/", "CSC148H1", ";", "/"] ] 

And if we run expand_one_or a second time on the resulting list, we get

[ ["CSC148H1", ",", "CSC165H1", "/", "CSC148H1", ";", "/"], 
["CSC148H1", ",", "CSC240H1", "/", "CSC148H1", ";", "/"] 
["CSC150H1", ",", "CSC165H1", "/", "CSC240H1", "/", "CSC148H1", ";", "/"] ] 

我曾经做到这一点的代码是：

c = [ ["CSC148H1", "/", "CSC150H1", ",", "CSC165H1", "/", "CSC240H1", "/", 
"CSC148H1", ";", "/"] ] 
d = [['CSC148H1', ',', 'CSC165H1', '/', 'CSC240H1', '/', 'CSC148H1', ';', '/'], ['CSC150H1', ',', 'CSC165H1', '/', 'CSC240H1', '/', 'CSC148H1', ';', '/']] 
def expand_one_or(course_lists): 
    accumulator = [] 
    k = 0 
    for lis in course_lists: 
     for i in range(len(lis)): 
      if lis[i] == '/' and i != len(lis) and k == 0: 
       if lis[i - 1].isalnum() and lis[i + 1].isalnum(): 
        k = 1 
        list1 = lis[:i] + lis[(i + 2):] 
        list2 = lis[i + 1:] 
        accumulator.append(list1) 
        accumulator.append(list2) 

       else: 
        lis.remove(lis[i]) 
        k = 1 
    return accumulator 

对于第一次迭代此代码的功能，但没有按”为第二个工作。

因此，举例来说，如果我们给的功能就像一个列表：

[ ["CSC148H1", "/", "CSC150H1", ",", "CSC165H1", "/", "CSC240H1", "/", 
"CSC148H1", ";", "/"] ] 

也应该给输出

[['CSC148H1', ',', 'CSC165H1', '/', 'CSC240H1', '/', 'CSC148H1', ';', '/'], ['CSC150H1', ',', 'CSC165H1', '/', 'CSC240H1', '/', 'CSC148H1', ';', '/']] 

现在，如果我们把功能该输出代码再次它应该给：

[ ["CSC148H1", ",", "CSC165H1", "/", "CSC148H1", ";", "/"], 
["CSC148H1", ",", "CSC240H1", "/", "CSC148H1", ";", "/"] 
["CSC150H1", ",", "CSC165H1", "/", "CSC240H1", "/", "CSC148H1", ";", "/"] ] 

问题是，当我第一次运行该功能它给了我适当的输出。但是，当我第二次运行它时，它给了我：

[['CSC148H1', ',', 'CSC165H1', '/', 'CSC148H1', ';', '/'], ['CSC240H1', '/', 'CSC148H1', ';', '/']] 

而这是错误的输出。

Answer 1

试试这个：

def split_list(l, i): 
    return [l[:i] + l[i+2:], l[:i-1] + l[i+1:]] 

def expand_one_or(course_lists): 
    k = 0 
    accumulator = [] 
    for lis in course_lists: 
    if k == 0 and '/' in lis: 
     k = 1 
     i = lis.index('/') 
     if i > 0 and i < len(lis)-1 and lis[i-1].isalnum() and lis[i+1].isalnum(): 
     accumulator += split_list(lis, i) 
     k = 1 
     else: 
     accumulator.append(lis[:i] + lis[i+1:]) 
    else: 
     accumulator.append(lis) 
    return accumulator