Iterating through a list using function

Question

I want to iterate through a list in python and printing it with the word 'hello' after it. However, I am not getting the desired output.

The code reads a text file which has numeric ID's. I have created a list of the read ID and used a for loop to iterate through it. Following is my code:

def read_file():
 pmid_s = []
 file_object = open("file.txt", "r", encoding='cp1252')
 pmid =file_object.read()
 pmid_s.append(pmid)
 for pmid in pmid_s:
    return(pmid)

def driver(pmid):
 print("hello"+pmid) 

def main():
 pmid= read_file
 driver(pmid)

if __name__ == '__main__':
   main()

The desired output is as follows in new line:

hello1
hello2
hello3
hello4
hello5

What output do you get? Why are you calling driver instead of print? And why are you redefining the print function?! — Blorgbeard
– Blorgbeard, Commented Apr 10, 2019 at 15:10
You just appending the whole bunch to the list, i.e. one big string returned by read(). You could try pmid_s = list(file_object). This is going to give you the lines. — a_guest
– a_guest, Commented Apr 10, 2019 at 15:10
What exactly is read_file supposed to do? You read the entire contents into one variable, append that to an empty list, then iterate over the singleton list. The entire function could be simplified to read_file = lambda: open(...).read(). — chepner
– chepner, Commented Apr 10, 2019 at 15:12
@chepner the function read_file is supposed to read data from a text file and append it to an empty list which needs to be iterated for the print function to print hello+pmid — RRg
– RRg, Commented Apr 10, 2019 at 15:17

ionut · Accepted Answer · 2019-04-10 15:27:57Z

2

If I understand your question correctly, you need to use driver(pmid) instead of return(pmid). Also you can split what you read directly using the split() method, and there's no need to append after that. See below:

def read_file():
    pmid_s = []
    file_object = open("file.txt", "r", encoding='cp1252')
    pmid_s =file_object.read().split()
    for pmid in pmid_s:
        driver(pmid)


def driver(pmid):
    print("hello {} \n ".format(pmid))


def main():
    pmid= read_file()


if __name__ == '__main__':
    main()

I'm also assuming that the numbers you read are separated by space

edited Apr 10, 2019 at 15:27

answered Apr 10, 2019 at 15:12

ionut

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2 Comments

glibdud Over a year ago

You might want to actually run your code and verify that it does what is expected before posting it.

quamrana Over a year ago

Just some reformatting of your program @ionut, and you're there! Yes! Now your program runs! Well done.

chepner · Accepted Answer · 2019-04-10 15:24:48Z

1

You have a file consisting of a series of integers, one per line. A file iterator yields the lines of the file. You can build the list by iterating over the file itself.

def read_file(fname):
    with open(fname, "r", encoding='cp1252') as f:
        return [line.strip() for line in f]

def driver(s):
    print("hello" + s)

def main():
    for num in read_file("file.txt"):
        driver(s)

if __name__ == "__main__":
    main()

If you want to do it lazily, make read_file a generator function.

def read_file(fname):
    with open(fname, "r", encoding='cp1252') as f:
        for line in f:
            yield line.strip()

This only ever reads a single line of the file into memory at a time, when a consumer tries to read the next item from the resulting generator.

edited Apr 10, 2019 at 15:24

answered Apr 10, 2019 at 15:17

chepner

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