Convert string to list of mixed float, int and str knowing the format in Python

Question

Consider a simple string like '1.5 1e+05 test 4'. The format used in Python 2.7 to generate that string is '%f %e %s %i'. I want to retrieve a list of the form [1.5,100000,'test',4] from my input string knowing the string formatter. How can I do that (Python 2.7 or Python 3)?

Thanks a lot,

Ch.

`import parse, format_string='{:1f} {:.2e} {:s} {:d}' pn=format_string.format(1.5,100000,'test',4) parsed=parse.parse(format_string, pn)` Does not work — ChrisB, Nov 22 '17 at 22:06
Have you considered [`ast.literal_eval`](https://docs.python.org/3/library/ast.html#ast.literal_eval)? — Patrick Haugh, Nov 22 '17 at 22:17
In your format string, replace `{:s}` with `{}`. For some reason this works — Jerfov2, Nov 22 '17 at 22:22
@PatrickHaugh That's generally a bad idea, unless you absolutely need it — Jerfov2, Nov 22 '17 at 22:24
@Jerfov2 Thanks for the tip, it works well, this remains however a mystery why `{:s}` didn't work — ChrisB, Nov 22 '17 at 22:27

score 1 · Accepted Answer · answered Nov 22 '17 at 22:31

1

Use the parse module. This module can do 'reverse formatting'. Example:

from parse import parse

format_str = '{:1f} {:.2e} {} {:d}' 
data = [1.5, 100000, 'test', 4]
data_str = format_str.format(*data)
print(data_str) # Output: 1.500000 1.00e+05 test 4
parsed = parse(format_str, data_str)
print(parsed) # Output: <Result (1.5, 100000.0, 'test', 4) {}>
a, b, c, d = parsed # Whatever

answered Nov 22 '17 at 22:31

Jerfov2

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@ChrisB You're welcome! If you liked the answer, accept it – Jerfov2 Nov 22 '17 at 22:51

Convert string to list of mixed float, int and str knowing the format in Python

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