如果元素包含特定字符，则从列表或集合中删除元素

Question

我收到了一个包含月份的 txt 文件，我打开并填写到一个列表或集合中。我需要遍历列表并删除任何带有字母“r”或“R”的月份。我尝试使用集合和列表，但不断收到 RuntimeError。这是我使用集合的代码：

monthList = {}

def main():
    monthList = fillList()
    print(monthList)
    removeRMonths(monthList)

def fillList():
    infile = open("SomeMonths.txt")
    monthList = {line.rstrip() for line in infile}
    return monthList

def removeRMonths(monthList):
    for month in monthList:
        for ch in month:
            if ch == "r" or ch == "R":
                monthList.remove(month)
    print(monthList)

main()

我收到的错误是：

Traceback (most recent call last):
  File "/Users/hwang/Desktop/Week7.py", line 115, in <module>
    main()
  File "/Users/hwang/Desktop/Week7.py", line 99, in main
    removeRMonths(monthList)
  File "/Users/hwang/Desktop/Week7.py", line 107, in removeRMonths
    for month in monthList:
RuntimeError: Set changed size during iteration
>>> 

这是我尝试使用列表的代码：

monthList = ()

def main():
    monthList = fillList()
    print(monthList)
    removeRMonths(monthList)

def fillList():
    infile = open("SomeMonths.txt")
    monthList = (line.rstrip() for line in infile)
    return monthList

def removeRMonths(monthList):
    for month in monthList:
        for ch in month:
            if ch == "r" or ch == "R":
                monthList.remove(month)
            else:
                continue
    print(monthList)

main()

我的错误是：

Traceback (most recent call last):
  File "/Users/hwang/Desktop/Week7.py", line 117, in <module>
    main()
  File "/Users/hwang/Desktop/Week7.py", line 99, in main
    removeRMonths(monthList)
  File "/Users/hwang/Desktop/Week7.py", line 110, in removeRMonths
    monthList.remove(month)
AttributeError: 'generator' object has no attribute 'remove'

这些错误的原因是什么？我尝试用谷歌搜索每条错误消息，但找不到任何我能理解的答案。我是初学者，所以我会很感激一个容易理解的答案。提前致谢！

Answer 1

您不应该在迭代时修改列表集。

首先使用列表推导式来创建列表。然后使用另一个列表推导过滤掉元素。最后，在过滤完成后使用切片分配更新原列表。

monthList = ()

def main():
    monthList = fillList()
    print(monthList)
    removeRMonths(monthList)

def fillList():
    infile = open("SomeMonths.txt")
    monthList = [line.rstrip() for line in infile]
    return monthList

def removeRMonths(monthList):
    monthList[:] = [month for month in monthList if 'r' not in month.lower()]
    print(monthList)