将csv文件读取到python ValueError：无法将字符串转换为float

Question

Any help with this would be appreciated. Please keep in mind that I am a beginner in Python. This is the portion of the code that I am having trouble with:

__author__ = 'peter'



from datetime import datetime, timedelta
import csv


TICKER='CHTR'
STDEV_FILE = TICKER + '_stdev.csv'
TRADES_FILE = TICKER + '_trades.csv'
DATETIME_CSV_FORMAT = '%Y%m%d %H:%M:%S'

def read_data(csv_filename):
  result = {}
  with open(csv_filename, 'rb') as csvfile:
     reader = csv.reader(csvfile, delimiter=',', quotechar='|')
     header = reader.next()
     #print 'HEADER',header
     for row in reader:
        new_data=None
        if len(row)==6: # this is a QUOTES file
          ticker, date, time, price, rtn, standard = row
          rtn = float(rtn)
          standard = float(standard)
          new_data = [rtn, standard]
        else: # assume this is a TRADES file otherwise
          ticker, date, time, price, size = row
          price = float(price)
          size = int(size)
          new_data = [price, size]

        date_object = datetime.strptime(date +' '+time, DATETIME_CSV_FORMAT)
        if not ticker in result:
          result[ticker]=[]
        result[ticker].append([date_object] + new_data)
  return result

vol = read_data(STDEV_FILE)
trades = read_data(TRADES_FILE

)

When I run it this is the error I recieve:

Traceback (most recent call last):
  File "/home/peter/PycharmProjects/Vol/Vol.py", line 39, in <module>
    vol = read_data(STDEV_FILE)
  File "/home/peter/PycharmProjects/Vol/Vol.py", line 25, in read_data
    standard = float(standard)
ValueError: could not convert string to float: #DIV/0!

I have run this on other csv files and had no trouble.

Here is a small sample of the csv file:

SYMBOL  DATE    TIME    PRICE          RTN                     STDEV
-----------------------------------------------------------------------
CHTR    20130718    9:30:00 124.66  0                0
-----------------------------------------------------------------------
CHTR    20130718    9:30:00 124.66  0                0.0005674559
-----------------------------------------------------------------------
CHTR    20130718    9:30:00 124.56  -0.0008025039        0.0004539101
-----------------------------------------------------------------------
CHTR    20130718    9:30:00 124.54  -0.0001605781        0.0001135459
-----------------------------------------------------------------------
CHTR    20130718    9:30:00 124.54  0                0.0070177722
-----------------------------------------------------------------------
CHTR    20130718    9:31:56 123.310 -0.0099246286        0.011065531
-----------------------------------------------------------------------
CHTR    20130718    9:34:05 124.018 0.0057243955         0.0040363557
-----------------------------------------------------------------------

Ultimately I would like to plot the standard deviation on y axis and seconds from midnight on x axis. Any help would be appreciated.

Answer 1

The issue is that you are trying to convert the string "#DIV/0' to a float. Obviously this is not possible. The cause of this is attempting to divide by zero somewhere in your excel/csv sheet. Look back through your excel sheet and see if anything is divided by zero and change it.

Alternately you could implement a simple if statement:

if standard == '#DIV/0':
    print 'Error'
else:
    standard = float(standard)

EDIT: Some references: http://office.microsoft.com/en-us/excel-help/correct-a-div-0-error-HP010066245.aspx

Answer 2

Instead of "if standard == '#DIV/0':", it might be easier and more readable to do:

 if standard.isdigit():
      standard = float(standard)
 else:
      # error code

str.isdigit() will check all the characters in 'str' to see if they are digits.