Keyboard keycodes
Below there is the table of mnemonic codes referring to keyboard keys. You can use them as argument of key() command to check if a particular key has been pressed from users instead of type in the ASCII code.

k_backspace
k_tab
k_clear
k_return
k_pause
k_escape
k_esc
k_space
k_exclaim
k_quotedbl
k_hash
k_dollar
k_ampersand
k_quote
k_leftparen
k_rightparen
k_asterisk
k_plus
k_comma
k_minus
k_period
k_slash
k_colon
k_semicolon
k_less
k_equals
k_greater
k_question
k_at
k_leftbracket
k_backslash
k_rightbracket
k_caret
k_underscore
k_backquote
k_delete
Numbers:
k_1
k_2
k_3
k_4
k_5
k_6
k_7
k_8
k_9
k_0
Arrows
k_up
k_down
k_right
k_left
k_insert
k_home
k_end
k_pageup
k_pagedown

Keypad:
k_kp0
k_kp1
k_kp2
k_kp3
k_kp4
k_kp5
k_kp6
k_kp7
k_kp8
k_kp9
k_kp_period
k_kp_divide
k_kp_multiply
k_kp_minus
k_kp_plus
k_kp_enter
k_kp_equals
Function Keys
k_f1
k_f2
k_f3
k_f4
k_f5
k_f6
k_f7
k_f8
k_f9
k_f10
k_f11
k_f12
k_f13
k_f14
k_f15
k_numlock
k_capslock
k_scrollock
k_rshift
k_lshift
k_rctrl
k_lctrl
k_ralt
k_lalt
k_rmeta
k_lmeta
k_lsuper Left "Windows" key
k_rsuper Right "Windows" key
k_mode "Alt Gr" key
k_compose Multi-key compose key
k_help
k_print
k_sysreq
k_break
k_menu
k_powe Power Macintosh power key
k_euro Some European keyboards
k_undo Atari keyboard has Undo