Dynamic variable from function in Python

Question

var 1 is constantly changing with every new line that is written in the csv file. Any suggestion how can I get the value outside of the function. This example does not work for me. I updated my code and added second function which is exactly the same but is reading another file. Now I only get print from the first function only. If I disable the first function I can get the print from the second function. Is there a way to print both of them or maybe three or four if I add later new functions ?

import sys
import time
import datetime
import os


class Application():

    def loop_one(self):

       filename = 'Test.csv'
       mycsv = open(filename, 'r')
       mycsv.seek(0, os.SEEK_END)

       while 1:
            time.sleep(1)
            where = mycsv.tell()
            line = mycsv.readline()

       if not line:
            mycsv.seek(where)

       else:
           arr_line = line.split(',')
           var1 = arr_line[5]
           mydate = datetime.datetime.now()
           print var1, mydate.strftime("%H:%M:%S:%f")
           return var1

    def loop_two(self):

       filename2 = 'Test2.csv'
       mycsv2 = open(filename2, 'r')
       mycsv2.seek(0, os.SEEK_END)

       while 1:
            time2.sleep(1)
            where2 = mycsv2.tell()
            line2 = mycsv2.readline()

       if not line2:
            mycsv2.seek(where2)

       else:
           arr_line2 = line2.split(',')
           var2 = arr_line2[5]
           mydate2 = datetime.datetime.now()
           print var2, mydate.strftime("%H:%M:%S:%f")
           return var2

s = Application()
var1 = s.loop_one()
var2 = s.loop_two()

I tried var1 = s.loop_one() and then print var1 but got nothing — manev
– manev, Commented Dec 1, 2016 at 23:33
Are you sure your indentation is correct? Should your if and else statement be within the while loop? — Kevin M Granger
– Kevin M Granger, Commented Dec 1, 2016 at 23:35

Randy Arguelles · Accepted Answer · 2016-12-02 01:19:02Z

You can declare a variable inside the init function so you can use that anywhere

class A(object):
    def __init__(self):
        self.x = 'Hello'

    def method_a(self, foo):
        print self.x + ' ' + foo

In your case you can do something like this (not tested)

class Application():

    def __init__(self):

       self.filename = 'Test.csv'
       self.mycsv = open(self.filename, 'r')
       self.mycsv.seek(0, os.SEEK_END)
       self.var1 = ''

    def loop_one(self):
        while 1:
            time.sleep(1)
            where = self.mycsv.tell()
            line = self.mycsv.readline()

            if not line:
                self.mycsv.seek(where)
                # you need a break here or somewhere :D

            else:
                arr_line = line.split(',')
                self.var1 = arr_line[5]
                mydate = datetime.datetime.now()
                print self.var1, mydate.strftime("%H:%M:%S:%f")
                return self.var1

s = Application()
s.loop_one()

sdvd · Accepted Answer · 2016-12-02 00:09:20Z

You have move your if else block inside the for loop otherwise your code will stuck in infinite loop.

import sys
import time
import datetime
import os

class Application():

    def loop_one(self):

       filename = 'Test.csv'
       mycsv = open(filename, 'r')
       mycsv.seek(0, os.SEEK_END)

       while 1:
            time.sleep(1)
            where = mycsv.tell()
            line = mycsv.readline()

            if not line:
                 mycsv.seek(where)

            else:
                arr_line = line.split(',')
                var1 = arr_line[5]
                mydate = datetime.datetime.now()
                print var1, mydate.strftime("%H:%M:%S:%f")
                return var1

s = Application()
s.loop_one()

Emmanuel Mtali · Accepted Answer · 2016-12-02 00:15:35Z

0

Accessing var1 outside the function

class Application:
    var1 = None

    def loop_one(self):
        # Code
        while True:
            # Your code
            if not line:
                # Code
            else:
                global var1
                # Code
                var1 = arr_line[5]

    # Then you can access it via
    def show():
        print(var1)

answered Dec 2, 2016 at 0:15

Emmanuel Mtali

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