在 Python 中从字符串中提取数字
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Extract Number from String in Python
提问by Umair
I am new to Pythonand I have a String, I want to extract the numbers from the string. For example:
我是新手Python，我有一个字符串，我想从字符串中提取数字。例如：
str1 = "3158 reviews"
print (re.findall('\d+', str1 ))
Output is ['4', '3']
输出是 ['4', '3']
I want to get 3158only, as an Integer preferably, not as List.
我只想得到3158，最好是整数，而不是列表。
采纳答案by Vishnu Upadhyay
You can filterthe string by digitsusing str.isdigitmethod,
您可以使用方法filter按数字字符串str.isdigit，
>>> int(filter(str.isdigit, str1))
3158
回答by 6502
If the format is that simple (a space separates the number from the rest) then
如果格式那么简单（一个空格将数字与其余数字分开）那么
int(str1.split()[0])
would do it
会做的
回答by hellobenallan
Your regex looks correct. Are you sure you haven't made a mistake with the variable names? In your code above you mixup total_hotel_reviews_stringand str.
您的正则表达式看起来正确。你确定你没有弄错变量名吗？在你的代码你上面的mixuptotal_hotel_reviews_string和str。
>>> import re
>>> s = "3158 reviews"
>>>
>>> print(re.findall("\d+", s))
['3158']
回答by Irshad Bhat
This code works fine. There is definitely some other problem:
这段代码工作正常。肯定还有其他问题：
>>> str1 = "3158 reviews"
>>> print (re.findall('\d+', str1 ))
['3158']
回答by M.Danilchenko
There may be a little problem with code from Vishnu's answer. If there is no digits in the string it will return ValueError. Here is my suggestion avoid this:
毗湿奴的回答中的代码可能有一点问题。如果字符串中没有数字，它将返回 ValueError。这是我的建议，避免这种情况：
>>> digit = lambda x: int(filter(str.isdigit, x) or 0)
>>> digit('3158 reviews')
3158
>>> digit('reviews')
0
回答by Yang Qi
My answer does not require any additional libraries, and it's easy to understand. But you have to notice that if there's more than one number inside a string, my code will concatenate them together.
我的答案不需要任何额外的库，而且很容易理解。但是您必须注意，如果字符串中有多个数字，我的代码会将它们连接在一起。
def search_number_string(string):
index_list = []
del index_list[:]
for i, x in enumerate(string):
if x.isdigit() == True:
index_list.append(i)
start = index_list[0]
end = index_list[-1] + 1
number = string[start:end]
return number
回答by Eugene Yarmash
To extract a single number from a string you can use re.search(), which returns the first match (or None):
要从字符串中提取单个数字，您可以使用re.search()，它返回第一个匹配项（或None）：
>>> import re
>>> string = '3158 reviews'
>>> int(re.search(r'\d+', string).group(0))
3158
回答by Bernard
IntVar = int("".join(filter(str.isdigit, StringVar)))
回答by thund
Above solutions seem to assume integers. Here's a minor modification to allow decimals:
以上解决方案似乎假设整数。这是一个允许小数的小修改：
num = float("".join(filter(lambda d: str.isdigit(d) or d == '.', inputString)
(Doesn't account for - sign, and assumes any period is properly placed in digit string, not just some english-language period lying around. It's not built to be indestructible, but worked for my data case.)
（不考虑 - 符号，并假设任何句号都正确放置在数字字符串中，而不仅仅是一些英文句号。它不是为了坚不可摧，而是适用于我的数据案例。）
回答by Ayush Singh
Use this, THIS IS FOR EXTRACTING NUMBER FROM STRING IN GENERAL.
使用这个，这通常用于从字符串中提取数字。
To get all the numeric occurences.
获取所有出现的数字。
*split function to convert string to list and then the list comprehension which can help us iterating through the list and is digit function helps to get the digit out of a string.
*split 函数将字符串转换为列表，然后列表理解可以帮助我们遍历列表，并且是数字函数有助于从字符串中获取数字。
getting number from string
从字符串中获取数字
use list comprehension+isdigit()
使用列表理解+isdigit()
test_string = "i have four ballons for 2 kids"
print("The original string : "+ test_string)
# list comprehension + isdigit() +split()
res = [int(i) for i in test_string.split() if i.isdigit()]
print("The numbers list is : "+ str(res))
To extract numeric values from a string in python
在python中从字符串中提取数值
*Find list of all integer numbers in string separated by lower case characters using re.findall(expression,string)method.
*使用re.findall(expression,string)方法查找以小写字符分隔的字符串中所有整数的列表。
*Convert each number in form of string into decimal number and then find max of it.
*将字符串形式的每个数字转换为十进制数，然后找到它的最大值。
import re
def extractMax(input):
# get a list of all numbers separated by lower case characters
numbers = re.findall('\d+',input)
# \d+ is a regular expression which means one or more digit
number = map(int,numbers)
print max(numbers)
if __name__=="__main__":
input = 'sting'
extractMax(input)
