scanning user input in python

direction = input("enter a direction: ") if direction != "quit" and direction != "go north" and direction != "go south" and direction != "go east" and direction != "go west" and direction != "go up" and direction != "go down" and direction != "look": print ("please enter in the following format, go (north,east,south,west,up,down)") elif direction == "quit": print ("OK ... but a small part of you may never leave until you have personally saved Muirfieland from the clutches of evil .. Bwahahahahahah (sinister laugh) ... the game should then end.") elif direction == "look": print ("You see nothing but endless void stretching off in all directions ...") else: print ("You wander of in the direction of " + direction) 

i need to know how to do this in python. i need to scan user inputs first 2 letters for example

i = user_input #user inputs go ayisgfdygasdf 

i need it to be able to scan the user input, check if the first 2 letters are go, and if they are go but it doesnt recognise the second word which in this case is "ayisgfdygasdf" then to print "sorry, i cant do that"

4 Answers

He could also try using:

 directions.split() 

But it may require to use try/except in some cases.

For more information about split and methods try using:

 dir(directions) 

to see what methods object directions have

or:

 help(directions.split) 

to see help about a specific method (in this case method split of object directions)

You can access characters of a string in python by index using the [] notation. You can check the first two character in a string by typing user_input[:2]. This code will include all characters up to, but not including the index typed. So this notation will include user_input[0] and user_input[1]. You can then check if user_input[:2] is equal to 'go' or not, and continue from there.

Hope this helped.

Instead try using:

direction = sys.stdin.readlines() 

It may require you to ctrl+D after you are done but you will be able to capture so much more.

Also, to get the subarray you can then you can even check:

direction[:2] != "go" 

or alternatively, for more readable code:

if not direction.startswith("go"): 

Also I'd recommend, for making your code more readable,

defined_direction = frozenset(["quit", "go north", "go south"]) if( direction not in defined_direction): print "please enter...." 

You can index the individual characters of your input:

if direction[:2] == "go": print "Sorry, I can't do that." 

However, trying assign an if-else branch to each possible input is typically a bad choice... It becomes difficult to maintain very quickly.

A cleaner approach in this case might be to define a dictionary with valid input as follows:

input_response = {"quit":"OK ... but", "go north": "You wander off north", \ "go south": "You wander off south"} # etc 

You could then re-write your code to something like:

try: print input_response[direction] except KeyError: if direction[:2] == "go": print "Sorry, I can't do that." else: print ("please enter in the following format...")