"Tim Chase" <py*********@tim.thechases.com> wrote in message
news:ma***************************************@pyt hon.org...
Are there existing "quiet" conversion functions? Kin of
int() and float()?
My aim would be to call a function that would guarntee that
the result was of the defined type, choosing sensible
defaults if needed. Example problems include:
int("3.14")
int(None)
int(__builtins__)
int("hello")
For the 2nd through 4th examples, I'd consider zero to be a
reasonable response from this phantasmic function. For the
first one, it would be sensible to return "3". Wrapping it
in a float() call:
int(float("3.14"))
seems a little smarter, but is still more overhead than a
mythical justGiveMeAStinkingInt() call.
At the moment, I've churned my own helper functions, of the form
def CInt(value):
try:
value = int(value)
except (ValueError, TypeError):
try:
value = int(float(value))
except (ValueError, TypeError):
value = 0
return value
def CFloat(value):
try:
value = float(value)
except (ValueError, TypeError):
value = 0
return value
Is there some set of preexisting functions that do this sort
of "sensible" conversions without griping about crazy values
passed to them? If not, are there other exceptions that
might be thrown that I haven't considered yet?
It would also be handy to have a CBool that is a little
smarter about strings (though I18N'ing it becomes a little
trickier...)
CBool("Yes") # returns True
CBool("No") # returns False
CBool("True") # returns True
CBool("False") # returns False
CBool("Y") # returns True
CBool("N") # returns False
CBool("T") # returns True
CBool("F") # returns False
CBool(None) # returns False
CBool(1) # returns True for any non-zero
CBool(0) # returns False
CBool("oui") # returns True?
CBool("si") # returns True?
CBool("Nyet") # returns False?
Any tips in this direction as well?
My first shot is something like the rather ugly
def CBool(value):
if value:
# There's prob. a better way
# to check if it's a string...
if type(value) is type(""):
return (value[0].lower() in
"ytos")
else:
return True
else:
return False
Thanks for any tips or hints towards deuglification,
-tkc
Here are two approaches, one defines a function, the other a class.
-- Paul
"""
CBool("Yes") # returns True
CBool("No") # returns False
CBool("True") # returns True
CBool("False") # returns False
CBool("Y") # returns True
CBool("N") # returns False
CBool("T") # returns True
CBool("F") # returns False
CBool(None) # returns False
CBool(1) # returns True for any non-zero
CBool(0) # returns False
CBool("oui") # returns True?
CBool("si") # returns True?
CBool("Nyet") # returns False?
"""
# define CBool as a method
def CBool(arg):
trueStrings = set( "Yes yes YES Y True true TRUE T Oui oui OUI Si si
SI".split() )
falseStrings = set( "No no NO N False false FALSE F Nyet nyet
NYET".split() )
if isinstance(arg,basestring):
if arg in trueStrings:
return True
elif arg in falseStrings:
return False
else:
raise ValueError, "could not determine boolean-ness of %s" % arg
else:
return bool(arg)
# or define CBool as a class
class CBool(object):
trueStrings = set( "Yes yes YES Y True true TRUE T Oui oui OUI Si si
SI".split() )
falseStrings = set( "No no NO N False false FALSE F Nyet nyet
NYET".split() )
def __init__(self,arg):
self.initarg = arg
if isinstance(arg,basestring):
if arg in self.trueStrings:
self.boolVal = True
elif arg in self.falseStrings:
self.boolVal = False
else:
raise ValueError, "could not determine boolean-ness of %s" %
arg
else:
self.boolVal = bool(arg)
def __nonzero__(self):
return self.boolVal
def __str__(self):
return "CBool(%s):%s" % (str(self.initarg),bool(self))
def testCBool(s):
print s,'->',CBool(s)
testCBool("Yes") # returns True
testCBool("No") # returns False
testCBool("True") # returns True
testCBool("False") # returns False
testCBool("Y") # returns True
testCBool("N") # returns False
testCBool("T") # returns True
testCBool("F") # returns False
testCBool(None) # returns False
testCBool(1) # returns True for any non-zero
testCBool(-1) # returns True for any non-zero
testCBool(6.02E23) # returns True for any non-zero
testCBool(0) # returns False
testCBool(0.0) # returns False
testCBool("oui") # returns True?
testCBool("si") # returns True?
testCBool("Nyet") # returns False?
testCBool("Purple") # returns True
The class version prints out the following (the function gives similar
output):
Yes -> CBool(Yes):True
No -> CBool(No):False
True -> CBool(True):True
False -> CBool(False):False
Y -> CBool(Y):True
N -> CBool(N):False
T -> CBool(T):True
F -> CBool(F):False
None -> CBool(None):False
1 -> CBool(1):True
-1 -> CBool(-1):True
6.02e+023 -> CBool(6.02e+023):True
0 -> CBool(0):False
0.0 -> CBool(0.0):False
oui -> CBool(oui):True
si -> CBool(si):True
Nyet -> CBool(Nyet):False
Purple ->
Traceback (most recent call last):
File "CBool.py", line 75, in ?
testCBool("Purple") # returns True
File "CBool.py", line 56, in testCBool
print s,'->',CBool(s)
File "CBool.py", line 45, in __init__
raise ValueError, "could not determine boolean-ness of %s" % arg
ValueError: could not determine boolean-ness of Purple
