How to extract a floating number from a string

Question

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

User · Answer

Another approach that may be more readable is simple type conversion. I've added a replacement function to cover instances where people may enter European decimals:

>>> for possibility in "Current Level: -13.2 db or 14,2 or 3".split():
...     try:
...         str(float(possibility.replace(',', '.')))
...     except ValueError:
...         pass
'-13.2'
'14.2'
'3.0'

This has disadvantages too however. If someone types in "1,000", this will be converted to 1. Also, it assumes that people will be inputting with whitespace between words. This is not the case with other languages, such as Chinese.

User · Answer

Python docs has an answer that covers   -  and exponent notation  scanf   Token      Regular Expression  e   E   f   g      -     d     d       d    eE  -    d     i                  -    0 xX   dA-Fa-f   0 0-7    d     This regular expression does not support international formats where a comma is used as the separator character between the whole and fractional part  3 14159   In that case  replace all    with      in the above float regex                           Regular Expression International float      -     d       d         d    eE  -    d

User · Answer

I think that you ll find interesting stuff in the following answer of mine that I did for a previous similar question   https   stackoverflow com q 5929469 551449  In this answer  I proposed a  pattern that allows a regex to catch any kind of number and since I have nothing else to add to it  I think it is fairly complete

User · Answer

If your float is always expressed in decimal notation something like   gt  gt  gt  import re  gt  gt  gt  re findall   d    d     Current Level  13 4 db      13 4     may suffice   A more robust version would be    gt  gt  gt  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       gt  Would print         Current is something else   Level  is something else   1e 100 is a float   db is something else

User · Answer

You may like to try something like this which covers all the bases  including not relying on whitespace after the number    gt  gt  gt  import re  gt  gt  gt  numeric const pattern   r             -      optional sign                              d      d       1  12  123 etc 9 1 etc 98 1 etc                                d          1  12  123  etc 1 12 123 etc                     followed by optional exponent part if desired              Ee    -    d                   gt  gt  gt  rx   re compile numeric const pattern  re VERBOSE   gt  gt  gt  rx findall   1  12 9 1 98 1 1  12  1 12      1     12    9 1    98 1    1     12     1    12    gt  gt  gt  rx findall  -1  1 2e9  2E 09 -2e-9     -1     1    2e9     2E 09    -2e-9    gt  gt  gt  rx findall  current level  -2 03e 99db     -2 03e 99    gt  gt  gt    For easy copy-pasting   numeric const pattern     -             d      d           d              Ee    -    d       rx   re compile numeric const pattern  re VERBOSE  rx findall  Some example  Jr  it  was  23 between 2 3 and 42 31 seconds

User · Answer

re findall r  -    d     d   d     Current Level  -13 2 db or 14 2 or 3     as described above  works really well  One suggestion though   re findall r  -    d     d   -    d     Current Level  -13 2 db or 14 2 or 3 or -3     will also return negative int values  like -3 in the end of this string

User · Answer

You can use the following regex to get integer and floating values from a string   re findall r   d   d      hello -34 42  34 478m 88 cricket -44 3      34    42    34 478    88    44 3     Thanks Rex

[python] How to extract a floating number from a string

Examples related to python

Examples related to regex

Examples related to floating-point

Examples related to data-extraction