Cannot convert string to float

Question

I am getting information from a csv, I need to take a field which in theory is a float, but can come empty, I'm this function which takes the row [i] where the float is, and should return the float,

def fun(x):
    if not(x):
        x=0
        x=float(x)
    else:
        x = float(x)
    return x

but when i try it throws me this error tells me "float () argument must be a string or a number"

try to fix your formatting, that's not legal python as it is. — Russia Must Remove Putin, Jan 17 '15 at 01:38
@PadraicCunningham for example fun(row[11]), and row[11] in the csv is empty, — Hook, Jan 17 '15 at 01:41
yes but are you always positive row[11] will be able to be parsed as a float? I think a try/except would be much better — Padraic Cunningham, Jan 17 '15 at 01:42
@PadraicCunningham for example, height could be like this, first line empty, but second line, 14.4, and so — Hook, Jan 17 '15 at 01:50
so what type **is** `x`? Add a `print(type(x))` as the very first line of `fun`, and show us what it says!-) — Alex Martelli, Jan 17 '15 at 02:58

Hugh Bothwell · Accepted Answer · 2015-01-17T03:13:38.073

1

Ok, how about

def fn(x):
    try:
        return float(x)
    except (ValueError, TypeError):
        return 0.0

edited Jan 17 '15 at 03:13

answered Jan 17 '15 at 01:39

Hugh Bothwell

55,315
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still tells me "float() argument must be a string or a number" – Hook Jan 17 '15 at 01:46
@Tabbz, are you passing a list, a tuple, etc,,? You need to `print row[11] `and see exactly what you are passing – Padraic Cunningham Jan 17 '15 at 01:48
@Tabbz,`except (ValueError,TypeError):` will catch the TypeError but you should really see what row[11] is when you get the error. What does` print row[11]` show right before the error? – Padraic Cunningham Jan 17 '15 at 01:52
im printing like this print 'row[11] '+str(row[11]) print 'row[12] '+str(row[12]) print 'row[13] '+str(row[13]), just you can know what im printing, but if i print only row[11] prints like " " – Hook Jan 17 '15 at 01:53
what exactly are you trying to cast to float? – Padraic Cunningham Jan 17 '15 at 01:55
row[11] are weight, in the csv several fields of this are empty, but others have numbers, the problem is those fields that are empty – Hook Jan 17 '15 at 01:58
1

ok so just catch the TypeError also, that will catch the empty strings `except (ValueError,TypeError):` – Padraic Cunningham Jan 17 '15 at 01:58

score -1 · Answer 2 · answered Jan 17 '15 at 03:57

-1

def fun(x):
    try:
        x = float(x)
    except ValueError:
        x = 0
    return x

print fun("1")
print fun(' ')

Output:

1.0
0

answered Jan 17 '15 at 03:57

f.rodrigues

3,499
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Cannot convert string to float

2 Answers2