[Tkinter] Two text files in Text widget (python 3)

[Larz60+]

import os

# make sure in code directory
os.chdir(os.path.dirname(__file__))

with open('loc1.txt') as loc1, open('loc2.txt') as loc2:
    head = ['Date', 'Value 1', 'Value2']
    print(f'{head[0]:15} {head[1]:10} {head[2]:10}')
    while True:
        line1 = loc1.readline()
        if len(line1) == 0:
            break
        line1 = line1.strip().split()
        line2 = loc2.readline()
        line2 = line2.strip().split()
        print(f'{line1[0]:15} {line1[1]:10} {line2[1]:10}')

results:

Output:
Date            Value 1    Value2
21/06/18        -0.7       -0.7
22/06/18        -0.5       -0.5
06/07/18        -0.7       -0.8
13/07/18        -0.6       -0.7
20/07/18        -0.3       -0.3
27/07/18        -0.5       -0.7
10/08/18        -1.2       -1.0
17/08/18        -0.5       -0.5
24/08/18        -0.3       -0.3
21/09/18        -0.2       -0.2
28/09/18        -0.4       -0.5
17/10/18        -0.1       -0.3

you can add the gui code to insert into your widget
This code uses f-string (python 3.6 and newer)