Empty string detection in my Python?

Question

This blows my mind. What am I missing?

I am trying to detect if a cell in an Excel sheet is empty or not. But none of the tests seem to work in the way I expect. I would expect that the simple "not idkt" test would detect both empty strings and None, but no... In fact, it seems like None is not detected by - well - any of the tests, because in the third row, that's what is getting printed.

Code:

def getFromExcelSheet():
    wb = load_workbook("input.xlsx")
    idkts = [];
    idktRows = get_worksheet_as_list(wb.get_sheet_by_name('Inputs'))
    # print "Got these idkts" 
    for row in idktRows:
        # print row[0]
        idkt = str(row[2]).strip()
        filename = str(row[3]).strip()
        if idkt == None:
            print "Idkt == none"

        if idkt is None:
            print "Idkt is none"

        if idkt == u"":
            print "Idkt is ''"

        if idkt != u"":
            print "Idkt is !=''"

        if not idkt:
            print "not IDKT"

        if idkt:
            print "idkt"

        print idkt

Output

Idkt is !=''
idkt
3398041577

Idkt is !=''
idkt
3498100937

Idkt is !=''
idkt
None

What does it say if you print repr(idkt) on the last line? — thebjorn
– thebjorn, Commented Nov 20, 2012 at 8:40
if the None has ' around it, it is a string (and not the None constant...) — thebjorn
– thebjorn, Commented Nov 20, 2012 at 8:48

tzaman · Accepted Answer · 2012-11-20 08:54:07Z

4

idkt isn't empty, it's a string containing the word 'None'. Here's your issue:

idkt = str(row[2]).strip()

row[2] is a None, which becomes 'None' when you call str on it. Try this:

if idkt == 'None': print 'yay!'

You'd be better off testing for emptiness before the string conversion:

idkt = str(row[2]).strip() if row[2] else None

edited Nov 20, 2012 at 8:54

answered Nov 20, 2012 at 8:44

tzaman

48k11 gold badges93 silver badges118 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

bradley.ayers · Accepted Answer · 2012-11-20 08:50:32Z

1

The problem is that you're converting the cells to strings, and then comparing the result to the Python's None (which is not a string).

I assume you're using openpyxl in which case you should access the value of the cell via .value, e.g.

idkt = row[2].value

You will then have a standard Python object (str/int/None etc) that represents that data within the cell. You should use this value for your non-empty check, and it will behave the way you originally expected:

if idkt not in ('', None):  # remember bool(0) == False
    ...

edited Nov 20, 2012 at 8:50

answered Nov 20, 2012 at 8:45

bradley.ayers

38.5k14 gold badges98 silver badges101 bronze badges

Collectives™ on Stack Overflow

Empty string detection in my Python?

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related