Extract float number from string with 're.findall'

Question

I want to extract a float number from the string:

"{start Time : 123.24,"

I tried using re.findall like this:

number = re.findall("\d.\d", lines[i])

Where lines[i] is above string.

Which only returns only 3.2 (first decimal place).

How can I extract float number regardless its number of decimal places?

Your input certainly looks like JSON content, so using regex might not be the best approach. Instead, look into Python's built in `json` library for how you might _parse_ your content to extract the float. — Tim Biegeleisen, Aug 28 '20 at 09:41
@deceze Well `{start Time : 123.24,` certainly looks like at least a _broken_ JSON fragment to me. — Tim Biegeleisen, Aug 28 '20 at 09:47

score 5 · Answer 1 · answered Aug 28 '20 at 09:43

5

As noted by Tim, if your input is JSON, parse it as JSON; don’t faff around with regex.

But a simple fix to your regex is the use of quantifiers (and use raw string literals, and escape the dot):

number = re.findall(r"\d+\.\d+", lines[i])

answered Aug 28 '20 at 09:43

Konrad Rudolph

At 457K, you can't possibly be wrong, right? +1 – Tim Biegeleisen Aug 28 '20 at 09:48

score 0 · Answer 2 · edited Aug 28 '20 at 09:55

0

My solution with regex. But it would only exstract one float number from the string.

import re
str_in = "{start Time : 123.24,"

regex = re.compile(r"[0-9]+.[0-9]*")

elem = (re.search(regex, str_in))

result = float(elem.group())

edited Aug 28 '20 at 09:55

Fabián Montero

answered Aug 28 '20 at 09:49

Marcin

Note that this wouldn't work if the floats were written in exponential notation. – jottbe Aug 28 '20 at 09:58

score 0 · Answer 3 · answered Aug 28 '20 at 09:49

If you don't want to use JSON, try the following regex:

\d+\.\d+

The + means 1 or more. Which will capture all the numbers.

So your code would look like this:

number = re.findall("\d+\.\d+", lines[i])

A good place to learn/test regexes is this website: https://pythex.org/

3 Answers3