前导零后的逗号

Question

Desired result (final values in float):

00 → 0.0

20 → 20.0

15 → 15.0

05 → 0.5

003 → 0.03

01 → 0.1

How would I be supposed to do this? The initial values are a string, but when I convert it to float the zeroes disappear. Are there any pre-made functions for this?

Answer 1

This is easily done with regular expressions.

In [1]: import re

In [2]: def reformat_numbers(num):
   ...:     return float(re.sub('^0', '0.', num))
   ...: 

In [3]: [reformat_numbers(n) for n in ['00', '20', '15', '05', '003', '01']]
Out[6]: [0.0, 20.0, 15.0, 0.5, 0.03, 0.1]

Answer 2

Another simple implementation taking care of exception as well:

import math
x = ['00', '20', '15', '05', '003', '01', '0']

def convert_to_float(val):
    try:
        if val[0] == '0':
            if len(val[1:]) > 0:
                decimal_part = float(val[1:])
                val = decimal_part / math.pow(10, len(val[1:]))
            else:
                val = 0.0
        else:
            val = float(val)
    except ValueError:
        print('Not a number')
    return val

for val in x:
    print(convert_to_float(val))

Output:

0.0
20.0
15.0
0.5
0.03
0.1
0.0

Answer 3

From your examples, it seems like you can just add a decimal after the first char then cast it to float. Eg

my_num = '002'
my_num = float(my_num[0] +  '.' + my_num[1:])

As always when casting, wrap it in a try/except in case the input is not castable.

Answer 4

I'm not sure what you're trying to do, because you give no specification, only examples. But this works:

for num in ("00", "20", "15", "05", "003", "01"):
    if num[0] == '0':
        print('0.' + num[1:])
    else:
        print(num + '.0')

Tested:

$ python3 convert.py 
0.0
20.0
15.0
0.5
0.03
0.1

Answer 5

You can use float.

For example:

a = "20"

y = float(a)