CODEWITHSUNDEEP
pythonstringlistfloating-point
Jacob Baum
Jacob Baum

Reputation: 27

Convert a String Into a Float From List In Python

I have a long, un-grouped list and I am trying to convert the decimal numbers from strings to floats. However, they exist in a list that has other strings and integers. Here is an example of what I am working with:

List1 = ['01/01/2020', 'AType', '4.30', '789.33', '02/01/2020', 'BType', '342.77', '84', '03/01/2020', 'CType', '2', '245.22', etc, etc, etc,]

I am aware of the way to convert strings into integers [int(f) if f.isdigit() else f for f in listone] but that does not seem to work with [float(x.strip(' "')) if x.isdecimal() else x for x in listone]. How do I convert the decimal strings into floats?

Upvotes: 0

Views: 177

Answers (2)

Samwise
Samwise

Reputation: 71562

You might write a function that will convert the strings according to whatever rules you want, and then map it over the list:

from typing import Union

def convert_string(x: str) -> Union[str, int, float]:
    """Attempts to convert a string to an int or float.
    Returns the string unchanged if no conversion possible."""
    try:
        return int(x)
    except ValueError:
        pass
    try:
        return float(x)
    except ValueError:
        return x

>>> list(map(convert_string, ["foo", "1.21", "1"]))
['foo', 1.21, 1]

Practically speaking, I think it'd be better to group these values, perhaps into a NamedTuple?

>>> from typing import List, NamedTuple
>>> class Thingy(NamedTuple):
...     date: str
...     type: str
...     num1: float
...     num2: float
...
>>> def build_thingy(elements: List[str]) -> Thingy:
...     """Build a Thingy from input list of 4 elements.
...     Raises if the input list is not valid."""
...     [date, type, num1, num2] = elements
...     return Thingy(date, type, float(num1), float(num2))
...
>>> [build_thingy(List1[i:i+4]) for i in range(0, len(List1), 4)]
[Thingy(date='01/01/2020', type='AType', num1=4.3, num2=789.33),
 Thingy(date='02/01/2020', type='BType', num1=342.77, num2=84.0),
 Thingy(date='03/01/2020', type='CType', num1=2.0, num2=245.22)]

Upvotes: 1

Retardrino
Retardrino

Reputation: 63

Try using regex(import re) to isolate floats from your list

Upvotes: 0

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