file1 = ""
file2 = ""

file1entry = Entry().pack()
file2entry = Entry().pack()

def OpenFile1():
    name = askopenfilename(initialdir="C:/Users/",
                           filetypes=(("Text File", "*.txt"),
                                      ("All Files", "*.*")),
                           title="Choose a file."
                           )
    # Using try in case user types in unknown file or closes without choosing a file.
    try:
        with open(name, 'r') as UseFile:
            file1 = UseFile
            file1entry.text = file1
    except:
        print("No file exists")