Strings Not Converting to Float as Expected

Question

I'm facing a problem in converting str to float. I do like in this post but this time it's not working because I have numbers in this format:

5.50000e+000 5.50000e+001 5.50000e+002 5.50000e+003

If I change the format (for example using 5.5 55 550 5500) it works fine. The Traceback states only:

Traceback (most recent call last):
  File "phresREADER.py", line 27, in <module>
    tra = float(stri)
ValueError: could not convert string to float:

What can I do? Is there a specific command?

my code is:

my_line = f.readline() 
avg_energySTR = [str(i) for i in my_line.split(' ')]
for stri in avg_energySTR:
        tra = float(stri)

when I print avg_energySTR I get

['5.50000e+000', '5.50000e+001', '5.50000e+002', '5.50000e+003', '\n']

THE ANSWER IS IN THE KOJIRO'S COMMENT

works for me also, python 2.7, can you show us your output / trace back? — Kobi K, Apr 28 '14 at 14:58
Just tested in console on Python2.7 and Python3.3 `float('5.50000e+000')` outputs `5.5`, `float(5.50000e+000)` outputs `5.5`, even just typing in `5.50000e+000` outputs `5.5` — jshanley, Apr 28 '14 at 15:06
what is inside `avg_energySTR`?, you probably have a problem in the for statement. — Kobi K, Apr 28 '14 at 15:08
@user3254025 the content of `avg_energySTR`, that's what we need to see — Kobi K, Apr 28 '14 at 15:09
@user3254025 add `print(avg_energySTR)` before the `for` loop and post what you get. — jonrsharpe, Apr 28 '14 at 15:13
Do `split()` with no arguments: perhaps your whitespace is not just the `' '` character. — kojiro, Apr 28 '14 at 15:15
yep, @kojiro was right, you matched a `\n` newline character. — jshanley, Apr 28 '14 at 15:17

score 1 · Accepted Answer · answered Apr 28 '14 at 15:17

You have a '\n' at one of the list cells.

So when the iteration is trying to convert '\n' to float it raise an ValueError

Try this code:

avg_energySTR = "5.50000e+000 5.50000e+001 5.50000e+002 5.50000e+003"
avg_energySTR = [str(i) for i in avg_energySTR.split()]
avg_energy = []
for stri in avg_energySTR:
        tra = float(stri)
        avg_energy.append(tra)
print (avg_energy)

You can also just split at the for itself:

avg_energySTR = "5.50000e+000 5.50000e+001 5.50000e+002 5.50000e+003 \n"
avg_energy = []
for stri in avg_energySTR.split():
       .......

Or just `avg_energy = [float(stri) for stri in avg_energySTR.split()]` — kojiro, Apr 28 '14 at 15:19

score 1 · Answer 2 · answered Apr 28 '14 at 15:19

Change:

avg_energySTR = [str(i) for i in my_line.split(' ')]

To:

avg_energySTR = my_line.split()

From the comments, it appears that you have extra whitespace at the end of the line. If you use the default split algorithm (by passing no arguments, or by passing None), then trailing whitespace will be ignored.

Strings Not Converting to Float as Expected

2 Answers2