如何在Python字符串中查找子字符串

我有一个字符串列表，如下所示：

strings = [
  "On monday we had total=5 cars",
  "On tuesday we had total = 15 cars",
  "On wensdsday we are going to have total=9 or maybe less cars"
]

some_sentence = "We will use this sentence to get total=20 of cars."
new_total = "????" // it needs to get total=20 
for str in strings:
  // Here I want to replace `total=<value>` or `total = <value>` in every str with new_total
  new_string = "????"
  print(new_string)

我希望能够从这些字符串中找到并替换子字符串

我可以按如下方式查找并替换它（如果我有要替换的字符串）：

在这种情况下，它只匹配

total=5

。这不是我想要的

我想首先从一个句子中提取

total=

，不管它在

=

符号之前或之后是否有空格，然后将提取的值插入到其他句子中

因此，有如下情况：

strings = [
  "On monday we had total=5 cars",
  "On tuesday we had total = 15 cars",
  "On wensdsday we are going to have total=9 or maybe less cars"
]

some_sentence = "We will use this sentence to get total=20 of cars."
new_total = "????" // it needs to get total=20 
for str in strings:
  // Here I want to replace `total=<value>` or `total = <value>` in every str with new_total
  new_string = "????"
  print(new_string)

---

你知道我该怎么做吗？

你就快到了。在正则表达式中使用

\d+

代替硬编码的

5

：

import re

strings = [
  "On monday we had total=5 cars",
  "On thursday we had total = 15 cars",
  "On wendesday we are going to have total=9 or maybe less cars"
]

new_total = "total = 20"
for s in strings:
  new_string = re.sub(r"total\s?=\s?\d+", "{}".format(new_total), s)
  print(new_string)

# to extract the information you can use:
p = re.compile(r"(total\s?=\s?\d+)")
for s in strings:
  print( p.findall(s) )

输出：

On monday we had total = 20 cars
On thursday we had total = 20 cars
On wendesday we are going to have total = 20 or maybe less cars
['total=5']
['total = 15']
['total=9']

---

如果您确定您将有一个匹配项，您也可以使用

p.search（s）.group（0）

（它将返回字符串而不是列表）而不是

p.findall（s）

，

，如果您可以明确说明您想要做什么：“我想在

=

周围添加空格-登录

total=XXX

”。只需一小部分文字，您的问题就更容易理解。@Aran Fey我想从一个句子中获取子字符串

some_-句子=“我们将使用这个句子来获取总计=20辆车。”

无论等号前后是否有空格。然后将其添加到字符串列表中的每个字符串中，而不是

total=

或

total=

Oh，那么您首先要从一个句子中提取

total=XXX

，然后将提取的值插入到其他句子中？我现在明白了。但是你的问题在我看来非常不清楚。你应该试着澄清一下。（就像问题本身，而不是评论中一样。）@Aran Fey确实如此好啊但是我想从一个句子中得到

total=

some_-sense=“我们将使用这句话获得总共20辆车。”

。如何从某个句子中获得

total=20

？@Aran Fey如果您希望比赛前后的部分可以在单独的组中访问，那么

*

部分是有用的。但我删除了它们，因为它们在这里真的不是必需的。