Convert '0000-00-00' to 'flag' in python

Question

I want to convert some data of dates into the string after checking them in a specific range. I have first converted all data into type float so that it can provide output as dates format but when I applied this for the dates it shows:

a1 = float(a1)
ValueError: could not convert string to float: '0000-00-00'

My whole code is:

import xlrd
import os.path
from datetime import datetime

date_array = []

wb = xlrd.open_workbook(os.path.join('E:\Files','SummaryLease.xlsx'))

sh = wb.sheet_by_index(0)

for i in range(1,sh.nrows):

    a1 = sh.cell_value(rowx=i, colx=80)
    if a1 is '0000-00-00':
        date_array.append('flag')
    else:
        a1 = float(a1)
        a1_as_datetime = datetime(*xlrd.xldate_as_tuple(a1, wb.datemode))
        date_array.append(a1_as_datetime.date())

print(date_array)

How should I solve this?

Answer 1

Don't compare strings using is operator, use ==.

if a1 == '0000-00-00':
    date_array.append('flag')
else:
    a1 = float(a1)

You can read more about the difference here: Is there a difference between `==` and `is` in Python?