I have written a line editor which hopefully does what you are looking for. But it is a quick-and-dirty hack. It is Windows only and written with CPython 3.6.5 on Windows 10, so its use might be limited. It has been tested on codepage 1252 (ANSI Latin 1; Western European (Windows)) and codepage 65001 (utf-8). It is very basic and a bit sluggish as it is not speed-optimized. (I should rewrite it in C but I do not have the time.) It is hardly tested and poorly documented.
import msvcrt
import os
import sys
if os.name != 'nt':
raise NotImplementedError('This module works only on MS Windows!')
CTRL_00 = 0
CTRL_E0 = 224
KEY_BACKSPACE = 8
KEY_DELETE = 83 # CTRL
KEY_END = 79 # CTRL
KEY_ESC = 27
KEY_HOME = 71 # CTRL
KEY_INSERT = 82 # CTRL
KEY_LEFT = 75 # CTRL
KEY_RETURN = 13
KEY_RIGHT = 77 # CTRL
flush = sys.stdout.flush
write = sys.stdout.write
mode = ('[OVR]> ', '[INS]> ') # overwrite, insert
prefix = len(mode[0])
def _update_line(insert, source, length, line, target):
"""Write a new line and position the cursor.
source: previous cursor position
length: old line length
line: edited line
target: next cursor position
"""
write('\b' * source) # set cursor to start of line
write(' ' * length) # erase old line
write('\b' * length) # again, set cursor to start of line
write(mode[insert] + line[prefix:]) # write updated line
write('\b' * (len(line) - target)) # set cursor to new position
flush() # write buffer to screen
def mswin_line_edit(default_string, insert=True):
"""Edit a MS Windows CLI line."""
insert = insert
line = mode[insert] + default_string
count = len(line)
before = line[:count]
after = line[count:]
print(line, end='', flush=True)
cursor = count
while True:
key = msvcrt.getwch()
num = ord(key)
if num == KEY_ESC: # abort edit
return default_string
if num == KEY_RETURN: # finish edit
return line
if num == KEY_BACKSPACE: # delete character before cursor
if cursor > prefix:
before = line[:cursor - 1]
after = line[cursor:]
line = before + after
_update_line(insert, cursor, count, line, cursor - 1)
cursor -= 1
count = len(line)
elif num == CTRL_E0 or num == CTRL_00: # CTRL
ctrl = ord(msvcrt.getwch())
if ctrl == KEY_END: # set cursor after last character
if cursor < count:
before = line
after = ''
_update_line(insert, cursor, count, line, count)
cursor = count
elif ctrl == KEY_HOME: # set cursor before first character
if cursor > prefix:
before = ''
after = line
_update_line(insert, cursor, count, line, prefix)
cursor = prefix
elif ctrl == KEY_LEFT: # move cursor 1 character to the left
if cursor > prefix:
before = line[:cursor]
after = line[cursor:]
_update_line(insert, cursor, count, line, cursor - 1)
cursor -= 1
elif ctrl == KEY_RIGHT: # move cursor 1 character to the right
if cursor < count:
before = line[:cursor]
after = line[cursor:]
_update_line(insert, cursor, count, line, cursor + 1)
cursor += 1
elif ctrl == KEY_DELETE: # delete character after cursor
if cursor < count:
before = line[:cursor]
after = line[cursor + 1:]
line = before + after
_update_line(insert, cursor, count, line, cursor)
count = len(line)
elif ctrl == KEY_INSERT: # switch insert/overwrite mode
insert ^= True
_update_line(insert, cursor, count, line, cursor)
else: # ordinary character
before = line[:cursor] + key
if insert:
after = line[cursor:]
else:
after = line[cursor + 1:]
line = before + after
_update_line(insert, cursor, count, line, cursor + 1)
cursor += 1
count = len(line)
if __name__ == '__main__':
test_string = input('test string: ')
result = mswin_line_edit(test_string)
print(f'\n{result}')
