我想使用.replace函数替换多个字符串。

我目前有

string.replace("condition1", "")

但想要一些像

string.replace("condition1", "").replace("condition2", "text")

尽管这样的语法感觉不太好

正确的做法是什么?有点像在grep/regex中,你可以用\1和\2来替换某些搜索字符串的字段


当前回答

下面是另一种使用字典的方法:

listA="The cat jumped over the house".split()
modify = {word:word for number,word in enumerate(listA)}
modify["cat"],modify["jumped"]="dog","walked"
print " ".join(modify[x] for x in listA)

其他回答

注意:测试你的案例,见注释。

这里有一个例子,它在长弦上更有效,有许多小的替换。

source = "Here is foo, it does moo!"

replacements = {
    'is': 'was', # replace 'is' with 'was'
    'does': 'did',
    '!': '?'
}

def replace(source, replacements):
    finder = re.compile("|".join(re.escape(k) for k in replacements.keys())) # matches every string we want replaced
    result = []
    pos = 0
    while True:
        match = finder.search(source, pos)
        if match:
            # cut off the part up until match
            result.append(source[pos : match.start()])
            # cut off the matched part and replace it in place
            result.append(replacements[source[match.start() : match.end()]])
            pos = match.end()
        else:
            # the rest after the last match
            result.append(source[pos:])
            break
    return "".join(result)

print replace(source, replacements)

关键是要避免长字符串的多次连接。我们将源字符串切成片段,在我们形成列表时替换一些片段,然后将整个字符串连接回字符串。

这是我对这个问题的解决办法。我把它用在聊天机器人上,一次替换不同的单词。

def mass_replace(text, dct):
    new_string = ""
    old_string = text
    while len(old_string) > 0:
        s = ""
        sk = ""
        for k in dct.keys():
            if old_string.startswith(k):
                s = dct[k]
                sk = k
        if s:
            new_string+=s
            old_string = old_string[len(sk):]
        else:
            new_string+=old_string[0]
            old_string = old_string[1:]
    return new_string

print mass_replace("The dog hunts the cat", {"dog":"cat", "cat":"dog"})

这就成了猫捉狗

我的方法是首先将字符串标记化,然后决定每个标记是否包含它。

潜在地,如果我们可以假设一个hashmap/set的O(1)查找,可能会更好:

remove_words = {"we", "this"}
target_sent = "we should modify this string"
target_sent_words = target_sent.split()
filtered_sent = " ".join(list(filter(lambda word: word not in remove_words, target_sent_words)))

Filtered_sent现在是'应该修改字符串'

我需要一个解决方案,其中字符串可以被替换为正则表达式, 例如,通过将多个空格字符替换为一个空格字符来帮助规范化长文本。根据其他人(包括MiniQuark和mmj)的一系列答案,我得出了以下结论:

def multiple_replace(string, reps, re_flags = 0):
    """ Transforms string, replacing keys from re_str_dict with values.
    reps: dictionary, or list of key-value pairs (to enforce ordering;
          earlier items have higher priority).
          Keys are used as regular expressions.
    re_flags: interpretation of regular expressions, such as re.DOTALL
    """
    if isinstance(reps, dict):
        reps = reps.items()
    pattern = re.compile("|".join("(?P<_%d>%s)" % (i, re_str[0])
                                  for i, re_str in enumerate(reps)),
                         re_flags)
    return pattern.sub(lambda x: reps[int(x.lastgroup[1:])][1], string)

它适用于其他答案中给出的例子,例如:

>>> multiple_replace("(condition1) and --condition2--",
...                  {"condition1": "", "condition2": "text"})
'() and --text--'

>>> multiple_replace('hello, world', {'hello' : 'goodbye', 'world' : 'earth'})
'goodbye, earth'

>>> multiple_replace("Do you like cafe? No, I prefer tea.",
...                  {'cafe': 'tea', 'tea': 'cafe', 'like': 'prefer'})
'Do you prefer tea? No, I prefer cafe.'

对我来说,最重要的是你也可以使用正则表达式,例如只替换整个单词,或规范化空白:

>>> s = "I don't want to change this name:\n  Philip II of Spain"
>>> re_str_dict = {r'\bI\b': 'You', r'[\n\t ]+': ' '}
>>> multiple_replace(s, re_str_dict)
"You don't want to change this name: Philip II of Spain"

如果你想使用字典键作为普通字符串, 你可以在调用multiple_replace之前转义这些,例如使用下面的函数:

def escape_keys(d):
    """ transform dictionary d by applying re.escape to the keys """
    return dict((re.escape(k), v) for k, v in d.items())

>>> multiple_replace(s, escape_keys(re_str_dict))
"I don't want to change this name:\n  Philip II of Spain"

下面的函数可以帮助在你的字典键中找到错误的正则表达式(因为来自multiple_replace的错误消息不是很明显):

def check_re_list(re_list):
    """ Checks if each regular expression in list is well-formed. """
    for i, e in enumerate(re_list):
        try:
            re.compile(e)
        except (TypeError, re.error):
            print("Invalid regular expression string "
                  "at position {}: '{}'".format(i, e))

>>> check_re_list(re_str_dict.keys())

请注意,它没有链接替换,而是同时执行它们。这使得它更有效率,而不会限制它能做什么。为了模仿链接的效果,你可能只需要添加更多的字符串替换对,并确保这些对的预期顺序:

>>> multiple_replace("button", {"but": "mut", "mutton": "lamb"})
'mutton'
>>> multiple_replace("button", [("button", "lamb"),
...                             ("but", "mut"), ("mutton", "lamb")])
'lamb'

另一个例子: 输入列表

error_list = ['[br]', '[ex]', 'Something']
words = ['how', 'much[ex]', 'is[br]', 'the', 'fish[br]', 'noSomething', 'really']

期望的输出将是

words = ['how', 'much', 'is', 'the', 'fish', 'no', 'really']

代码:

[n[0][0] if len(n[0]) else n[1] for n in [[[w.replace(e,"") for e in error_list if e in w],w] for w in words]]