In Python 2.7: How can I split a number from a string

Question

My strings are something like that:

str1 = "3,5 of 5 stars"
str2 = "4 of 5 stars"

I want to extract the first number of each string.

Something like that:

str1 = 3,5
str2 = 4

The Problem is that the numbers are in two formats (int and float)

I hope you guys can help me

Thanks for your help

You use comma for floats? `str1 = 3,5` would translate in a tuple in Python not a float.. Will the generall format\pattern by `str = "X of Y stars"`? — Ma0, Jan 13 '17 at 13:56
@Ev.Kounis I suspect this is a localisation issue - a lot of countries use a comma as the decimal mark — asongtoruin, Jan 13 '17 at 14:01
@MSeifert yes they start always with a number (e.g. 3 of.., 3,5 of ..) — Christian Rommel, Jan 13 '17 at 14:02
@asongtoruin Fair enough but Python uses `.` dot. So in Python again 3,5 is **not** what you get when dividing 7 with 2 but rather `(3, 5)`; a tuple of two integers — Ma0, Jan 13 '17 at 14:05
@Ev.Kounis I know and agree with you - just trying to help highlight where the confusion may have arisen. — asongtoruin, Jan 13 '17 at 14:08

score 0 · Answer 1 · answered Jan 13 '17 at 14:00

string = "3 o 4 k 5"

for char in string:
    entry = ""
    try:
        entry = int(char)
    except:
        continue
    if entry != "":
        print entry
        break

Here's the explanation. The string holds the string. As the for loop begins, char is set to the first character in the string. The for loop attempts to convert the character into an integer. If it is successful, it means that it is the character is a number. In that case, it is the first number to be found, so it is outputted and the loop stops.

If the conversion fails, it will output an error (thus the except part) but since we are using try/except, the loop will skip to its next character immediately. The for loop will continue until a number has been found or there are no numbers in the string.

Gurupad Mamadapur · Answer 2 · 2017-01-13T14:14:25.970

0

I guess your string format is - X of Y stars

You can extract X in this way.

>>> my_str = "3,5 of 5 stars"
>>> my_str.strip().split(' ')[0]
'3,5'

Let's say you want to convert 3,5 to float to do some math on it then you first replace , with . and then wrap around float(...).

>>> float(my_str.strip().split(' ')[0].replace(',','.'))
3.5

edited Jan 13 '17 at 14:14

answered Jan 13 '17 at 14:01

Gurupad Mamadapur

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you can replace the `,` with a `.` – Ma0 Jan 13 '17 at 14:12

ospahiu · Accepted Answer · 2017-01-13T14:16:28.563

0

If there is a space before the "of", you can use (avoids regex):

>>> print [item.split()[0] for item in [str1, str2]]
['3,5', '4']

edited Jan 13 '17 at 14:16

answered Jan 13 '17 at 14:02

ospahiu

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Why does there have to be a space after the `"of"`? You probably mean before – Ma0 Jan 13 '17 at 14:09

score 0 · Answer 4 · answered Jan 13 '17 at 14:02

0

If the pattern of strings is always "X of Y stars" you can do the following:

str1 = "3,5 of 5 stars"
str2 = "4 of 5 stars"

lst = [str1, str2, ...]
nums = [float(x.split(' of ')[0].replace(',','.')) for x in lst]
print(nums)  # prints [3.5, 4.0]

answered Jan 13 '17 at 14:02

Ma0

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score 0 · Answer 5 · edited May 23 '17 at 10:29

To match numbers and floats (using the , delimiter) in a string you could use the re module:

>>> re.findall(r"[-+]?\d*\,\d+|\d+", "5,5 of 5 stars")
['5,5', '5']

>>> re.findall(r"[-+]?\d*\,\d+|\d+", "5,5 of 5 stars")[0]
'5,5'

>>> re.findall(r"[-+]?\d*\,\d+|\d+", "4 of 5 stars")[0]
'4'

I've used the regex from this StackOverflow answer (from @miku) but modified it to use , as delimiter instead of ..

In Python 2.7: How can I split a number from a string

5 Answers5