使用backspace删除字符

Question

我正在创建一个文本框类，其中包含一个更新其文本的方法。它以用户的键盘输入作为参数，keys。文本框类还具有一个属性text，它非常不言自明，它是它的文本。因此，我需要将用户输入添加到文本框的text中。除非用户输入一个退空格键(即'\x08')，否则我需要删除它前面的所有字母。但是当然，如果有两个连续的后置空间，这不像一个backspace会删除一个backspace，我需要删除两次。因此，现在您已经了解了情况，下面是我解决问题的方法：

        def update(self, keys):
            if len(keys) > 0:
                
                # I have a shift variable because when you modify a variable at the same time as
                # iterating through it, the index will off shift, so I need to reverse that
                shift = 0
                for i in range(len(keys)):
                    i -= shift
                    
                    # If there's a backspace
                    if keys[i] == '\x08':
                        # If it's the first character
                        if i == 0:
                            # Remove the last character from the text box's text
                            self.text = self.text[:-1]
                            # Get rid of the backspace from the user input
                            keys = keys[1:]
                            # reverse the off shift, or else the for loop will skip the second element
                            shift += 1
                            
                        else:
                            j = i
                            # Counts how many backspaces follow up consecutively
                            del_count = 1
                            while keys[j] != '\x08':
                                j -= 1
                                del_count += 1

                            # Adjusts the user's input
                            keys = keys[:j - del_count] + keys[i+1:]
                            shift += del_count
                      
                    
                self.text += keys
                print(self.text)

它几乎可以很好地工作，除非用户的输入是一个由多个后置空间跟踪的字符，否则我会得到一个索引错误。例如，如果用户输入(keys)是"a\x08\x08"，我将在if keys[i] == '\x08':上得到一个索引错误。这是什么原因？有人能给我一个解决办法吗？提前谢谢。

Answer 1

您不应该修改其循环中的可迭代性。

我在三个步骤中遇到了这个问题：

• 合并了text和keys first
• 计数和收集后台字符索引，并实现了普通字符
• 在合并对象中以反序

删除了这两种字符。

试试这个：

def update(text, keys):
    if keys:
        # Step 1: Merge both `key` and `texts`
        print(repr(text))
        text += keys
        print(repr(text))

        # Step 2: Count and collect `backspace` posision and `effected chars` position in reversed order
        backspace_posision = []
        char_deleted_position = []
        for i, char in enumerate(text[::-1]):
            _r_i = - i - 1

            if char == "\x08":
                backspace_posision.append(_r_i)
                print("backspace_posision:", backspace_posision)
            elif len(char_deleted_position) < len(backspace_posision):
                char_deleted_position.append(_r_i)
                print(char)
                print("char_deleted_position:", char_deleted_position)

        # Step 3: Remove them in reversed order
        texts = list(text)
        text_leng = len(texts)
        
        print(repr(texts))
        for _r_i in sorted(backspace_posision + char_deleted_position, reverse=True):
            i = text_leng + _r_i
            print(i)
            texts.pop(i)
            print(repr(texts))

        text = "".join(texts)
        print(repr(text))

示例输出如下所示

update("ABC", "D\x08\x08EFG\x08H\x08\x08")

# Original text
>>>'ABC'
# Merged
>>>'ABCD\x08\x08EFG\x08H\x08\x08'

# Collecting backspace and effected chars in reversed order
# Collecting backspace
>>>backspace_posision: [-1]
>>>backspace_posision: [-1, -2]

# Collecting effected chars
>>>H
>>>char_deleted_position: [-3]

# Collecting backspace
>>>backspace_posision: [-1, -2, -4]

# Collecting effected chars
>>>G
>>>char_deleted_position: [-3, -5]
>>>F
>>>char_deleted_position: [-3, -5, -6]

# Collecting backspace
>>>backspace_posision: [-1, -2, -4, -8]
>>>backspace_posision: [-1, -2, -4, -8, -9]

# Collecting effected chars
>>>D
>>>char_deleted_position: [-3, -5, -6, -10]
>>>C
>>>char_deleted_position: [-3, -5, -6, -10, -11]

# Iterate the merged text in reversed order and remove them
>>>['A', 'B', 'C', 'D', '\x08', '\x08', 'E', 'F', 'G', '\x08', 'H', '\x08', '\x08']
>>>12
>>>['A', 'B', 'C', 'D', '\x08', '\x08', 'E', 'F', 'G', '\x08', 'H', '\x08']
>>>11
>>>['A', 'B', 'C', 'D', '\x08', '\x08', 'E', 'F', 'G', '\x08', 'H']
>>>10
>>>['A', 'B', 'C', 'D', '\x08', '\x08', 'E', 'F', 'G', '\x08']
>>>9
>>>['A', 'B', 'C', 'D', '\x08', '\x08', 'E', 'F', 'G']
>>>8
>>>['A', 'B', 'C', 'D', '\x08', '\x08', 'E', 'F']
>>>7
>>>['A', 'B', 'C', 'D', '\x08', '\x08', 'E']
>>>5
>>>['A', 'B', 'C', 'D', '\x08', 'E']
>>>4
>>>['A', 'B', 'C', 'D', 'E']
>>>3
>>>['A', 'B', 'C', 'E']
>>>2
>>>['A', 'B', 'E']
>>>'ABE'