python regex prevent nonetype error [duplicate]

Question

I have code below that searches for a pattern and assigns the pattern to a variable num if the pattern exists.

for row1 in cursor1:
    try:
        m = re.search(r"^[0-9]+(?=\s)", row1[0])
        num = m.group()
    except Exception as e:
        pass

I then use the num variable in the code below:

z1=(item for item in numlist if item[6]==num and harversine.myhaversine(custx,custy,item[2],item[3])<150)

I would like to eliminate the num variable and compare text that matches the regex directly to item[6] as in if item[6]==re.search(r"^[0-9]+(?=\s)",row1[0]).group() But of course this will give me an error for the rows that don't have the pattern. How do I achieve what I am trying to do without getting the nonetype has no attribute group() error? PS: The overall code not shown here loops through rows, creates tuples and assigns necessary values based on fulfillment of the if statement. I want to change the regex matching part shown in the code for better performance because not all rows use the num variable. I want the regex to be run only for the rows that use this variable.

put the assignment of item[6] inside of a try block and the comprehension inside of your else block for the aforementioned try — R Nar
– R Nar, Commented Nov 20, 2015 at 21:21
"NoneType has no attribute group" - I'm sure you know how to check for None... — Karoly Horvath
– Karoly Horvath, Commented Nov 20, 2015 at 21:22
@R Nar unfortunately I can't go that route because item[6] is being generated inside the comprehension and I am using generators so I need it to be where it's at. — ketar
– ketar, Commented Nov 20, 2015 at 22:01
@Karoly Horvath I am sorry but I don't understand what you mean. — ketar
– ketar, Commented Nov 20, 2015 at 22:02
Do you want to assign value of num to item[6] or compare it in the if condition? — sudo bangbang
– sudo bangbang, Commented Nov 24, 2015 at 13:44

sudo bangbang · Accepted Answer · 2015-11-24 18:35:25Z

0

As Karoly Horvath has pointed out, you can make use of the fact that text that doesn't match returns None object

In [2]: m = re.search(r"^[0-9]+(?=\s)", row1[0])
Out [2]: None

You can use this in if condition

z1=(item for item in numlist if (re.search(r"^[0-9]+(?=\s)",row1[0]) and item[6]==re.search(r"^[0-9]+(?=\s)",row1[0]).group()) and harversine.myhaversine(custx,custy,item[2],item[3])<150)

return value of re.search(r"^[0-9]+(?=\s)",row1[0]) ie, None will evaluate to false making value of whole condition false.

answered Nov 24, 2015 at 18:35

sudo bangbang

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1 Comment

sudo bangbang Over a year ago

Pleasure to know it worked for you. I liked the bit where you corrected the typo in my edit

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