Is pred(elm) true for all elements?
With the default predicate, this is the same as Python 2.5’s all() function; i.e., it returns true if all elements are true.
>>> all(["A", "B"])
True
>>> all(["A", ""])
False
>>> all(["", ""])
False
>>> all(["A", "B", "C"], lambda x: x <= "C")
True
>>> all(["A", "B", "C"], lambda x: x < "C")
False
From recipe in itertools docs.
Is pred(elm) is true for any element?
With the default predicate, this is the same as Python 2.5’s any() function; i.e., it returns true if any element is true.
>>> any(["A", "B"])
True
>>> any(["A", ""])
True
>>> any(["", ""])
False
>>> any(["A", "B", "C"], lambda x: x <= "C")
True
>>> any(["A", "B", "C"], lambda x: x < "C")
True
From recipe in itertools docs.
Is pred(elm) false for all elements?
With the default predicate, this returns true if all elements are false.
>>> no(["A", "B"])
False
>>> no(["A", ""])
False
>>> no(["", ""])
True
>>> no(["A", "B", "C"], lambda x: x <= "C")
False
>>> no(["X", "Y", "Z"], lambda x: x <="C")
True
From recipe in itertools docs.
How many elements is pred(elm) true for?
With the default predicate, this counts the number of true elements.
>>> count_true([1, 2, 0, "A", ""])
3
>>> count_true([1, "A", 2], lambda x: isinstance(x, int))
2
This is equivalent to the itertools.quantify recipe, which I couldn’t get to work.
Return the value converted to the type, or None if error.
type_ may be a Python type or any function taking one argument.
>>> print convert_or_none("5", int)
5
>>> print convert_or_none("A", int)
None
A simpler way to define an exception with a fixed message.
Subclasses have a class attribute .message, which is used if no message is passed to the constructor. The default message is the empty string.
Example:
>>> class MyException(DeclarativeException):
... message="can't frob the bar when foo is enabled"
...
>>> try:
... raise MyException()
... except Exception, e:
... print e
...
can't frob the bar when foo is enabled