第二次迭代没有

Question

我要回答的问题是：

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", ";", "/"] ]

我用来做这件事的代码是：

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

此代码在第一次迭代中起作用，但在第二次迭代中不起作用。你知道吗

例如，如果我们给函数一个列表，比如：

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

它应该给出输出

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

现在，如果我们将这个输出代码再次放入函数中，它应该给出：

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

问题是当我第一次运行这个函数时，它会给我正确的输出。但是，当我第二次运行它时，它会给我：

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

这是错误的输出。你知道吗

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