while True:
input = raw_input("enter input: ")
result = useInput(input)
def useInput(input):
if input == "exit":
break #return 0 / quit / etc.. i want to break the while loop from within this function
I know I can put the "if logic" directly in the while loop, but I want it to be in the function. Is there a way to break a while loop from within a function called in the loop?
"if logic" directly in the while loop,, would be the most preferred way.Python has a cool feature in generators - these allow you to easily produce iterables for use with a for loop, that can simplify this kind of code.
def input_until(message, func):
"""Take raw input from the user (asking with the given message), until
when func is applied it returns True."""
while True:
value = raw_input(message)
if func(value):
return
else:
yield value
for value in input_until("enter input: ", lambda x: x == "exit"):
...
The for loop will loop until the iterator stops, and the iterator we made stops when the user inputs "exit". Note that I have generalised this a little, for simplicity, you could hard code the check against "exit" into the generator, but if you need similar behaviour in a few places, it might be worth keeping it general.
Note that this also means you can use it within a list comprehension, making it easy to build a list of results too.
Edit: Alternatively, we could build this up with itertools:
def call_repeatedly(func, *args, **kwargs):
while True:
yield func(*args, **kwargs)
for value in itertools.takewhile(lambda x: x != "exit",
call_repeatedly(raw_input, "enter input: ")):
...
I usually do this:
def getInput():
while True:
yield raw_input("enter input: ")
for input in getInput():
if input == 'exit':
break
result = useInput(input)
You can raise an exception and handle it outside of while ... but that will likely result in some confusing code ...
def useInput(in_):
if in_ == "exit":
raise RuntimeError
try:
while True:
input = raw_input("enter input: ")
result = useInput(input)
except RuntimeError:
pass
It's MUCH better to just return a boolean flag and then break or not depending on the value of that flag. If you're worried that you already have something you want to return, don't fret -- python will happily let your function return more than one thing:
def func()
...
return something,flag
while True:
something,flag = func()
if flag:
break
Well if its just aesthetics thats keeps you from putting it in the while loop then any of the above would work... not of fan of the try/except one though. Just know there isn't going to be any performance difference putting it in its own function though. Here's one that I believe also meets your requirements :-)
# you have to define the function first if your while isn't in a function
def UseInput():
input = raw_input("enter input: ")
if input == "exit":
return False
elif input == "pass":
return True
# Do stuff
return True
while UseInput():
pass
