Source code for mmf.utils.input

"""Input processing functions for simplifying input from the user.

These allow the user to enter a value or quit with ctrl-c and throw a
Cancel exception."""

__all__ = ['Cancel','Invalid','input','okay']

from mmf.utils.mmf_test import simulate_input, simulate_cancel

class Cancel(Exception):
    """Exception raised by input routines to signify that the user has
    cancelled the entry via ctrl-c rather than entered a value.
    >>> try:
    ...     raise Cancel
    ... except Cancel, c:
    ...     print "Caught Exception: " + str(c)
    Caught Exception: Cancelled.
    """
    def __init__(self,mesg="Cancelled."):
        Exception.__init__(self,mesg)

class Invalid(Cancel):
    """Exception raised by input routines to signify that the user has
    entered and invalid input.  This is a subclass of Cancel so that
    an invalud input can be used to cancel the input, but
    specializations can be made.
    >>> try:
    ...     raise Invalid
    ... except Invalid, c:
    ...     print "Caught Exception: " + str(c)
    Caught Exception: Invalid Input.
    """
    def __init__(self,mesg="Invalid Input."):
        Exception.__init__(self,mesg)

def input(varname="input",dtype=None,default=None,eval=None,
          raw_input=raw_input):
    """Prompts the user to input a variable.  The user can break out of
    the input with ctrl-c upon which a Cancel exception is raised.

    Return dtype(eval(raw_input(message))) where the message includes
    the variable name and defualt value (if provided).  Note that
    using eval is dangerous as it allows the user to execute arbitrary
    code.  A safe version of eval should be provided if security is a concern.
    
    If default is defined but dtype is not, then dtype = type(default).

    >>> input("c",dtype=float,eval=eval,raw_input=simulate_input("5.5+2.0"))
    c = : 5.5+2.0
    7.5
    >>> input("c",default=2.5,raw_input=simulate_input(""))
    c = (2.5): 
    2.5
    >>> try: input("c",raw_input=simulate_input(""))
    ... except Invalid, err: print str(err) + " (No default)"
    c = : 
    Invalid Input. (No default)
    >>> try:input("c",default=1.0,raw_input=simulate_input("abc"))
    ... except Cancel, err: print "Cancelled: " + str(err)
    c = (1.0): abc
    Cancelled: Invalid Input.
    >>> try: input("c",raw_input=simulate_cancel)
    ... except Cancel, err: print "Cancelled: " + str(err)
    c = : ^C
    Cancelled: Cancelled.
    """
    def noop(x):
        """Do nothing."""
        return x

    if default is not None:
        mesg = varname + " = (" + `default` + "): "
    else:
        mesg = varname + " = : "

    if dtype is None:
        if default is not None:   # If default is specified, use it to
            dtype = type(default) # define filter type
        else:
            dtype = noop
    
    if eval is None:
        eval = noop

    try:
        inp = raw_input(mesg)
    except:
        raise Cancel

    if 0 == len(inp):
        if default is None:
            raise Invalid
        else:
            inp = `default`
    try:
        v = dtype(eval(inp))
    except:
        raise Invalid

    return v

def okay(message="yes or no?",default=None,raw_input=raw_input):
    """Return True if the user responds with an affirmative, False
    otherwise, or throw a Cancel exception.  A default may be
    provided.
    
    >>> okay(raw_input=simulate_input("yes"))
    yes or no? yes
    True
    >>> okay(message="okay?",raw_input=simulate_input("n"))
    okay? n
    False
    >>> okay(default="yes",raw_input=simulate_input(""))
    yes or no? (yes): 
    True
    >>> okay(default="yes",raw_input=simulate_input(["blah","okay"]))
    yes or no? (yes): blah
    Invalid Response: Please answer "yes" or "no".
    yes or no? (yes): okay
    True
    >>> try:okay(raw_input=simulate_cancel)
    ... except Cancel, err: print "Cancelled: " + str(err)
    yes or no? ^C
    Cancelled: Cancelled.
    """
    NotDone = True;
    if default is not None:
        mesg = message + " (" + default + "): "
    else:
        mesg = message + " "

    while NotDone:
        try:
            inp = raw_input(mesg)
        except:
            raise Cancel
    
        if 0 == len(inp):
            inp = default
            
        inp = str.lower(inp)

        yes = map(str.lower,["yes","true","ok","okay","alright","y"])
        no = map(str.lower,["no","false","not","never","n"])

        if 0 < yes.count(inp):
            NotDone = False
            ans = True
        elif 0 < no.count(inp):
            NotDone = False
            ans = False
        else:
            print ('Invalid Response: Please answer "yes" or "no".')
    return ans