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I'm using python3 to make a very simple ebook viewer, that will take a document and display it, and allow the user to navigate with page up/down keys. Along with this, I intend to have the audio transcript of that document playing along, with its speed adjusted so that it syncs with the user's reading pace.

What I'm having trouble with is displaying the file - the cursor goes right to the end every time, and to reach the top of the file, I need to scroll up. I looked at print() documentation, and there isn't anything helpful there. Can anyone tell me if there is any construct in python that allows you to display long text on terminal such that the text is displayed from the beginning?

Bumble Bee
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  • It's more of a hack but you could do something like readlines into a list, `print [:50]` then on next button event, `print[50:100]` – Sushant Jul 18 '18 at 11:59
  • I don't think that could work. What if my user changes his terminal size? He'd be left with a lot of blank space or the same problem as before – Bumble Bee Jul 18 '18 at 12:07
  • Are you using Python 3? What OS are you using? And what are you using to read the page up/down key presses? Does it have to be in the terminal, or would it be ok to use a GUI, eg Tkinter, which is now bundled with the standard library? – PM 2Ring Jul 18 '18 at 12:21
  • I'm using python 3, on ubuntu 18.04, and am using pynput module to read keypress/releases. I was hoping to keep this project simple, preferably based on the terminal; but if there is any GUI based module that can display from the beginning with no muss, no fuss, then I'm game – Bumble Bee Jul 18 '18 at 12:28
  • Try tkinter or kivy then – Sushant Jul 18 '18 at 12:43

1 Answers1

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You can do this in a terminal, using a library like pynput to read the key press events. But it's much easier to use a GUI library that already does most of the work for you. And a GUI allows you to choose the font and text colour, gives you automatic word-wrapping, if desired, etc. Here's a short demo using Tkinter's Text widget. This program gets the file name from the command line.

import sys
import tkinter as tk

# Open the main window & start the Tcl interpreter
root = tk.Tk()

# Make a Frame to hold the Text widget and its Scrollbar
frame = tk.Frame(root)
frame.pack()

# Add the Scrollbar first so that it doesn't
# disappear when the window width is small
scrollbar = tk.Scrollbar(root)
scrollbar.pack(side=tk.RIGHT, fill=tk.Y)

# Add the Text widget
viewer = tk.Text(root, wrap="word", yscrollcommand=scrollbar.set)
viewer.pack(side=tk.RIGHT, fill=tk.BOTH, expand=True)

# Connect the Scrollbar to the Text widget
scrollbar.config(command=viewer.yview)

# Get the file name from the command line
fname = sys.argv[1]

# Read the text file and add its contents to the Text widget
with open(fname) as f:
    viewer.insert(tk.END, f.read())

root.mainloop()

You can navigate the file using the scroll bar, and if you click in the text you can also use the normal key commands like PageUp, PageDown, the arrow keys, Ctrl-Home & Ctrl-End to navigate.

However, the Text widget is editable. Hopefully, that's not a problem. And of course any changes made in the Text widget won't affect the original file (unless you save the Text data). You can disable editing, as discussed in Is there a way to make the Tkinter text widget read only? but the simple way to do that also disables all the key commands, and the ability to copy text.

PM 2Ring
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