Python: ValueError: invalid literal for float():

Question

I'm really new with python. So maybe my question is really basic...For my work I'm checking different parameters in a period of time. For the Beginning with Python I wanted to plot a simple List with daily measured Temperature-values for a month. In the List I've three splits like these following structure:

Day -TAB- Temperature -TAB- Nr

My Code:

import pylab as pl
import numpy as np

filename = "u_netCDF_write"
file = open(filename)
NoOfValues = 31                                                      

counter=0
data = []              
for line in file:                                                     
    if counter <= NoOfValues:                                          
         data.append(line.strip('\n').strip('\t').split(' '))            
         if len(data[-1]) == 4:                                         
            data[-1].pop(3)                                             
    counter+=1                                                          
x = np.linspace(0,30,31)                                                
data = np.transpose(data)                                             

for i in range(len(data[2])):                                           
   data[2][i] = float(data[2][i])-273.15

When I try to plot a Temperature-per-Day-Plot I get the Error-Message:

Traceback (most recent call last):
  File ".../.../unetCDFplot.py", line 43, in <module>
    data[2][i] = float(data[2][i])-273.15   
ValueError: invalid literal for float(): 03.07.2014

It looks like that the Code didn't transpose the Data. Why is that so? Can anybody help me? Thanks!

It looks like Python is trying to interpret the date as a floating decimal point, which of course doesn't work because it's a date, and not a number. — n1c9, Nov 20 '15 at 17:10

score 3 · Accepted Answer · answered Nov 23 '15 at 16:15

I solved my problem! So for anybody who has the same problem, here is what I did: I used

print(repr(data))

(thanks to Stephany Dionysio) to check every step in my code and understood that the problem was not the transpose-function, but the empty spaces in every line. After trying different methods to delete the empty spaces I saw that I couldn't delete an array in an array caused by 'data.append'. To get the values I needed I used pop() in the append method:

data.append(line.strip('\n').strip('\t').split(' ').pop(7))

Now my code works fine. Thank you for your good advices, they put me to the right way! :)

score 2 · Answer 2 · edited May 23 '17 at 12:26

2

I don't know the content of your "u_netCDF_write" file so it is reasonably dificult to debug it. But as the other post shows, it cloud be a non-printing character that's present in the value.

See if this helps python ValueError: invalid literal for float()

edited May 23 '17 at 12:26

Community

1
1

answered Nov 20 '15 at 17:14

SZD

81
4

score 0 · Answer 3 · answered Nov 20 '15 at 17:29

0

03.07.2014 cannot be a float. It looks like you're using the wrong data from your data list.

answered Nov 20 '15 at 17:29

LegendaryDude

562
8
23

Python: ValueError: invalid literal for float():

3 Answers3