如何从字符串中提取浮动数字 [英] How to extract a floating number from a string

问题描述

我有许多类似于 Current Level：13.4 db。的字符串，我只想提取浮点数。我说浮动，而不是小数，因为它有时是整体。 RegEx可以做到这一点，或者有更好的方法吗？

解决方案

>

 >>> import re 
>>> re.findall（\ d + \.\d +，Current Level：13.4 db。）
 ['13.4'] 
  

就足够了。

一个更健壮的版本可能是：

 >>> re.findall（r[ -  +]？\ d * \.\\\d\\ | \d +，当前级别：-13.2 db或14.2或3）
 ['-13.2'， '14.2'，'3'] 
  

如果您想验证用户输入，

  user_input =当前级别：1e100 db
 for user_input .split（）：
 try：
＃如果成功，你有（首先）浮动
打印浮动（令牌），是浮动
除了ValueError：
打印令牌，是别的东西
 
＃=>将打印... 
＃
＃当前是别的
＃级别：是别的
＃1e + 100是一个浮点数
＃db是别的
  

I have a number of strings similar to Current Level: 13.4 db. and I would like to extract just the floating point number. I say floating and not decimal as it's sometimes whole. Can RegEx do this or is there a better way?

解决方案

If your float is always expressed in decimal notation something like

>>> import re
>>> re.findall("\d+\.\d+", "Current Level: 13.4 db.")
['13.4']

may suffice.

A more robust version would be:

>>> re.findall(r"[-+]?\d*\.\d+|\d+", "Current Level: -13.2 db or 14.2 or 3")
['-13.2', '14.2', '3']

If you want to validate user input, you could alternatively also check for a float by stepping to it directly:

user_input = "Current Level: 1e100 db"
for token in user_input.split():
    try:
        # if this succeeds, you have your (first) float
        print float(token), "is a float"
    except ValueError:
        print token, "is something else"

# => Would print ...
#
# Current is something else
# Level: is something else
# 1e+100 is a float
# db is something else

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