Python: Extract multiple float numbers from string

Question

Forgive me, I'm new to Python.

Given a string that starts with a float of indeterminate length and ends with the same, how can I extract both of them into an array, or if there is just one float, just the one.

Example:

"38.00,SALE ,15.20"
"69.99"

I'd like to return:

[38.00, 15.20]
[69.99]

Answer 1

You could also use regex to do this

import re
s = "38.00,SALE ,15.20"
p = re.compile(r'\d+\.\d+')  # Compile a pattern to capture float values
floats = [float(i) for i in p.findall(s)]  # Convert strings to float
print floats

Output:

[38.0, 15.2]

Answer 2

def extract_nums(text):
    for item in text.split(','):
        try:
            yield float(item)
        except ValueError:
            pass

print list(extract_nums("38.00,SALE ,15.20"))
print list(extract_nums("69.99"))

---

[38.0, 15.2]
[69.99]

However by using float conversion you are losing precision, If you want to keep the precision you can use decimal:

import decimal

def extract_nums(text):
    for item in text.split(','):
        try:
            yield decimal.Decimal(item)
        except decimal.InvalidOperation:
            pass

print list(extract_nums("38.00,SALE ,15.20"))
print list(extract_nums("69.99"))

---

[Decimal('38.00'), Decimal('15.20')]
[Decimal('69.99')]

Answer 3

You said you're only interested in floats at the start and end of the string, so assuming it's comma-delimited:

items = the_string.split(',')
try:
    first = float(items[0])
except (ValueError, IndexError):
    pass
try:
    second = float(items[-1])
except (ValueError, IndexError):
    pass

We have to wrap the operations in exception handlers since the value might not be a valid float (ValueError) or the index might not exist in the list (an IndexError).

This will handle all cases including if one or both of the floats is omitted.