webhelpers.misc

Helpers that are neither text, numeric, container, or date.

Data processing

webhelpers.misc.all(seq[, pred])

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.

webhelpers.misc.any(seq[, pred])

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.

webhelpers.misc.no(seq[, pred])

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.

webhelpers.misc.count_true(seq[, pred])

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.

webhelpers.misc.convert_or_none(value, type_)

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

webhelpers.misc.flatten(iterable)

Recursively iterate lists and tuples.

Examples:

>>> list(flatten([1, [2, 3], 4]))
[1, 2, 3, 4]
>>> list(flatten([1, (2, 3, [4]), 5]))
[1, 2, 3, 4, 5]

Class-related and miscellaneous

class webhelpers.misc.NotGiven

A default value for function args.

Use this when you need to distinguish between None and no value.

Example:

>>> def foo(arg=NotGiven):
...     print arg is NotGiven
...
>>> foo()
True
>>> foo(None)
False

webhelpers.misc.subclasses_only(class_, it, exclude=None)

Extract the subclasses of a class from a module, dict, or iterable.

Return a list of subclasses found. The class itself will not be included. This is useful to collect the concrete subclasses of an abstract base class.

class_ is a class.

it is a dict or iterable. If a dict is passed, examine its values, not its keys. To introspect the current module, pass globals(). To introspect another module or namespace, pass vars(the_module_or_namespace).

exclude is an optional list of additional classes to ignore. This is mainly used to exclude abstract subclasses.

Exceptions and deprecation

webhelpers.misc.deprecate(message, pending=False, stacklevel=2)

Issue a deprecation warning.

message: the deprecation message.

pending: if true, use PendingDeprecationWarning. If false (default), use DeprecationWarning. Python displays deprecations and ignores pending deprecations by default.

stacklevel: passed to warnings.warn. The default level 2 makes the traceback end at the caller’s level. Higher numbers make it end at higher levels.

webhelpers.misc.format_exception(exc=None)

Format the exception type and value for display, without the traceback.

This is the function you always wished were in the traceback module but isn’t. It’s different from traceback.format_exception, which includes the traceback, returns a list of lines, and has a trailing newline.

If you don’t provide an exception object as an argument, it will call sys.exc_info() to get the current exception.

class webhelpers.misc.DeclarativeException(message=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

message = ''

class webhelpers.misc.OverwriteError(filename, message="not overwriting '%s'")

Refusing to overwrite an existing file or directory.