how to check if a string is in a certain format in python?

Question

I will have a string and I want to check that it is in the format "float, float, float, float". There will be 3 commas and four floats, I don't know how many decimal places long the floats are gonna be. so I want to check it without using re class. I need to extract all four floats after checking the string. so 3 floats before a comma and 1 last after comma.

I can't find a string function to do that. I have checked my python reference book and still can't find a method. I usually code in C++ and recently begun Python. Thank you for your help.

And what is wrong with re? Homework assignment forbids it?

Stephen Rauch
– Stephen Rauch ♦

2019-02-13 02:23:55 +00:00
Commented Feb 13, 2019 at 2:23 — Stephen Rauch
– Stephen Rauch ♦, Commented Feb 13, 2019 at 2:23
@Stephen Rauch kinda

Altaïr Ibn-La'Ahad
– Altaïr Ibn-La'Ahad

2019-02-13 02:28:52 +00:00
Commented Feb 13, 2019 at 2:28 — Altaïr Ibn-La'Ahad
– Altaïr Ibn-La'Ahad, Commented Feb 13, 2019 at 2:28

kerwei · Accepted Answer · 2019-02-13 02:54:52Z

1

Here's my attempt at your problem.

# Returns the list of four floating numbers if match and None otherwise
def four_float(str_input):
    # Split into individual floats
    lst = str_input.split(',')

    for flt in lst:
        # Check for the existence of a single dot
        d_parts = flt.strip().split('.')
        if len(d_parts) != 2:
            return None
        else:
            # Check that the chars on both sides of the dot are all digits
            for d in d_parts:
                if not d.isdigit():
                    return None

    return [float(n) for n in lst]

edited Feb 13, 2019 at 2:54

answered Feb 13, 2019 at 2:47

kerwei

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