CODEWITHSUNDEEP
pythonpython-3.xcsvvalueerror
RoboC
RoboC

Reputation: 75

How Can I Solve ValueError dtype Without Using An Exception

I am working on a program that is supposed to update employees salaries by %5 and %10 based on age:

import csv
infile = open('employee.csv')
csvreader = csv.reader(infile)

rows = []
for row in csvreader:
  rows.append(row)

for i in rows:
  if(int(i[2]) < 40):      #LINE CAUSING A PROBLEM
    i[3] = round((1.05 * float(i[3])) , 2)
  else:
    i[3] = round((1.10 * float(i[3])) , 2)

print('\n\nList after updation:')
#loop print the data on the compile
for row in rows:
  print(row)

#open file and write the updated data
with open('employeeUpdate.csv', 'w', encoding='UTF8', newline='') as f:
  writer = csv.writer(f)
  for row in rows:
    writer.writerow(row)

When I run it I get the following error:

ValueError                                Traceback (most recent call last)
---> 23   if(int(i[2]) < 40):
ValueError: invalid literal for int() with base 10: 'age'

Data Sample:

ID   employee name   age   salary
1    Sara Wales      33    60994
2    John Smith      42    78399
3    Michael Ousley  22    58000
4    Rami Elliot     50    88382

I double-checked the data type and it was an integer-->('age', dtype('int64'))

I tried with open ('employee.csv', r) as infile and changing the problem line to if int(float(i[2]) < 40): but they both did not work. It said cannot convert string to float. I don't know why it is reading the integer as a string.

But when I added an exception like this:

for i in rows:
  try:
    if (int(i[2]) < 40):
        i[3] = round((1.05 * int(i[3])) , 2)
    else:
        i[3] = round((1.10 * int(i[3])) , 2)
  except ValueError:
        print("")

It worked, so my question is why did it only work with the exception!, and is there a way I can have it done without the exception?

Upvotes: 0

Views: 1550

Answers (1)

Taku
Taku

Reputation: 33734

Since csv.reader() continuously reads a stream until EOF, it doesn't have a concept of a header row. For the first iteration of rows, i would always be the string header row. And you're trying to convert the text "age" into int which would Python to error.

Your try-except works because it simply masks the error raised from the first row and prints a blank line instead.

To fix it, simply skip a line from the file to not include the header row, or skip the first iteration when doing the int conversion.

with open('employee.csv') as infile:
    infile.readline()
    csvreader = csv.reader(infile)
    # do stuff with csvreader

When handling large datasets and doing complicated data manipulations, consider using the pandas library. The issue described here and dtype conversions would automatically be handled by pandas.

Upvotes: 1

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