formatting strings in list of lists

Question

I have this list of list

a = [['c', '1.3e-8', '4.5e-8'], ['h', '3.4e-5', '2.3e-7', '2.3e-5']]

I want to format the 'e' strings only as

a = [[ 'c', '0.000000013', '0.000000045'], ['h', '0.000034', '0.00000023', '0.000023']]

How can I do this in Python? Thanks!

what have you tried until now? Why does the second list in the first line have 4 elements and 3 in the second line? — marianosimone
– marianosimone, Commented Apr 18, 2014 at 1:07
Do the sublists always have the same structure (a single letter string, followed by numeric ones)? — Blckknght
– Blckknght, Commented Apr 18, 2014 at 1:12
And why does the result for '1.3e-9' evaluate to '0.00000' (5 sig figs), while '4.5e-8' evaluates to '0.00000045' (8 sig figs)? Can you make your specification more clear please? — SethMMorton
– SethMMorton, Commented Apr 18, 2014 at 1:23
this is just an example. Lists have same number of elements but the first element is not a float looking string where as others are float looking strings. I want to format the 'e' part of strings, but want to keep the first element of the list. I am very new in learning Python. Thanks for your comments and I hope I am able to explain what I intend to do. Best! — Habib
– Habib, Commented Apr 18, 2014 at 1:40
You still haven't addressed several of the problems with your expected output. Again, why does '1.3e-9' -> '0.00000' while '4.5e-8' -> '0.00000045'? Why do both '2.3e-7' and '2.3e-5' -> '0.00023'?? — Two-Bit Alchemist
– Two-Bit Alchemist, Commented Apr 18, 2014 at 1:58

Puffin GDI · Accepted Answer · 2014-04-18 04:05:45Z

1

If you sure only first element is not a float.

from decimal import Decimal

a = [['c', '1.3e-8', '4.5e-8'], ['h', '3.4e-5', '2.3e-7', '2.3e-5']]

for inx, rec in enumerate(a):
    a[inx] = [rec[0]] + ['{:.{precise}f}'.format(Decimal(val),
                precise=int(val[-1])+1) for val in rec[1:]]

print(a)

Output:

[['c', '0.000000013', '0.000000045'], ['h', '0.000034', '0.00000023', '0.000023']]

answered Apr 18, 2014 at 4:05

Puffin GDI

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1 Comment

Habib Over a year ago

Your code gives TypeError, "cannot concatenate 'str' and 'int' objects.

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