Searching for a string in a file with python

Question

I need to do pretty much what a 'grep -i str file' gives back but I have been hitting my head up against this issue for ages.

I have a func called 'siteLookup' that I am passing two parameters: str 's', and file_handle 'f'. I want to a) determine if there is a (single) occurrence of the string (in this example site="XX001"), and b) if found, take the line it was found in, and return another field value that I extract from that [found] line back to the caller. (it is a 'csv' lookup). I have had this working periodically but then it will stop working and I cannot see why.

I have tried all of the different 'open' options including f.readlines etc.

#example line: 'XX001,-1,10.1.1.1/30,By+Location/CC/City Name/'
#example from lookupFile.csv: "XX001","Charleston","United States"

sf = open('lookupFile.csv')

def siteLookup(s, f):
    site = s.split(',')[0].strip().upper()
    if len(site) == 5:
        f.seek(0)
        for line in f:
            if line.find(site)>=0:
                city = line.split(',')[1].strip('"').upper()
                return city
            # else site not found 
            return -1
    else:  # len(site) != 5
        return -1

city = siteLookup(line, sf)
print(city)
sf.close()

I am getting zero matches in this code. (I have simplified this example code to a single search). I am expecting to get back the name of the city that matches a 5 digit site code - the site code is the first field in the example "line".

Any assistance much appreciated.

Patrick Artner · Accepted Answer · 2019-04-18 21:09:14Z

1

Your return is wrongly indented - if the thing you look for is not found in the first line, it will return -1 and not look further.

Use with open(...) as f: to make your code more secure:

with open("lookupFile.csv","w") as f: f.write("""#example from lookupFile.csv: "XX001","Charleston","United States" """)

def siteLookup(s, f):
    site = s.split(',')[0].strip().upper()
    if len(site) == 5:
        f.seek(0)
        for line in f:
            if site in line:   # if site in line is easier for checking 
                city = line.split(',')[1].strip('"').upper()
                return city

        # wrongly indented - will return if site not in line
        # return -1

    # if too short or not found, return -1 - no need for 2 returns  
    return -1


line = 'XX001,-1,10.1.1.1/30,By+Location/CC/City Name/'

with open('lookupFile.csv') as sf:
    city = siteLookup(line, sf)
    print(city)

Output:

CHARLESTON

answered Apr 18, 2019 at 21:09

Patrick Artner

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1 Comment

netDesign8 Over a year ago

Thank you - tested & confirmed as working as desired!

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