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...definitions else: # Python 2 specific definitions if sys.platform == 'win32': # Windows specific definitions else: # Posix specific definitions Don't expect a checker to understand obfuscations like "".join(reversed(sys.platform)) == "xunil". Runtime or type checking? Sometimes there's code that must be seen by a type checker (or other static analysis tools) but should not be executed. For such situations the typing module defines a constant, TYPE_CHECKING, that is considered Tr...
...Definitions Construction Representing Properties Deriving new paths Joining Changing the path's final component Making the path relative Sequence-like access Querying Concrete paths API Constructing File metadata Path resolution Directory walking File opening Filesystem modification Discussion Division operator joinpath() Case-sensitivity Copyright Abstract This PEP proposes the inclusion of a third-party module, pathlib, in the standard library. The inclusion is proposed under the p...
...definition. Parameter.VAR_POSITIONAL - a tuple of positional arguments that aren't bound to any other parameter. This corresponds to a "*args" parameter in a Python function definition. Parameter.VAR_KEYWORD - a dict of keyword arguments that aren't bound to any other parameter. This corresponds to a "**kwargs" parameter in a Python function definition. Always use Parameter.* constants for setting and checking value of the kind attribute. replace(*, name=<optional>, kind=<option...
...constructor work with multiple wrappers per definition make it obvious what is happening; at the very least it should be obvious that new users can safely ignore it when writing their own code be a syntax "that ... [is] easy to remember once explained" not make future extensions more difficult be easy to type; programs that use it are expected to use it very frequently not make it more difficult to scan through code quickly. It should still be easy to search for all definitions, a particular de...
...constructors for container objects: s = set(word for line in page for word in line.split()) d = dict( (k, func(k)) for k in keylist) Generator expressions are especially useful with functions like sum(), min(), and max() that reduce an iterable input to a single value: max(len(line) for line in file if line.strip()) Generator expressions also address some examples of functionals coded with lambda: reduce(lambda s, a: s + a.myattr, data, 0) reduce(lambda s, a: s + a[3], data, 0) These s...
...definitions of PyModule_AddStringConstant and PyModule_AddObject if the Python version is less than 2.0, which provides compatibility with PyXML on Python 1.5.2. If the platform has a bogus definition for LONG_BIT (the number of bits in a long), an error will be reported at compile time. Fix bugs in _PyTuple_Resize() which caused hard-to-interpret garbage collection crashes and possibly other, unreported crashes. Fixed a memory leak in _PyUnicode_Fini(). Build issues ...
...constructors", small functions that are used in the creation of class members. Another interesting possibility is supporting forward references, i.e. references to Python symbols that are declared further down in the class body. The other, weaker, rationale is purely cosmetic: The current method for specifying a metaclass is by assignment to the special variable __metaclass__, which is considered by some to be aesthetically less than ideal. Others disagree strongly with that opinion. This PEP wi...
...definition indicates that the interpreter should collect all keyword arguments that do not correspond to other named parameters. However, Python does not preserved the order in which those collected keyword arguments were passed to the function. In some contexts the order matters. This PEP dictates that the collected keyword arguments be exposed in the function body as an ordered mapping. Motivation Python's **kwargs syntax in function definitions provides a powerful means of dynamically ha...
...constructor, Message.add_payload(), Utils.dump_address_pair(), Utils.decode(), Utils.encode() New deprecations: Generator.__call__(), Message.get_type(), Message.get_main_type(), Message.get_subtype(), the 'strict' argument to the Parser constructor. These will be removed in email 3.1. Support for Python earlier than 2.3 has been removed (see PEP 291). All defect classes have been renamed to end in 'Defect'. Some FeedParser fixes; also a MultipartInvariantViolationDefect will be added to messag...
...constructor. Image is a subclass of ImageMixin and will add a constructor that can resize and/or convert an image between different pixel formats. This is intended to provide a fast and efficient default implementation of the new protocol. ImageSize is a minor helper class. See below for details. Tkinter.PhotoImage will implement the new protocol (mostly through the ImageMixin class) and all the Tkinter methods that can receive an image will be modified the accept any object that implements ...
...constructor or to a replace() method. This is similar to the current situation with the instances that fall in the spring-forward gap. Such instances don't represent any valid time, but neither the constructors nor the replace() methods check whether the instances that they produce are valid. Moreover, this PEP specifies how various functions should behave when given an invalid instance. Affected APIs Attributes Instances of datetime.time and datetime.datetime classes will get a new attr...
...constructors: the class statement just calls the metatype of the first base (or that specified by the __metaclass__ variable), and this metatype's constructor looks for the most derived metatype. If that is itself, it proceeds; otherwise, it calls that metatype's constructor. (Ultimate flexibility: another metatype might choose to require that all bases have the same metatype, or that there's only one base class, or whatever.) (In [1], a new metaclass is automatically derived that is a subclas...
...definitions will be: integer ::= decimalinteger | octinteger | hexinteger | bininteger | oldoctinteger octinteger ::= "0" ("o" | "O") octdigit+ bininteger ::= "0" ("b" | "B") bindigit+ oldoctinteger ::= "0" octdigit+ bindigit ::= "0" | "1" For Python 3.0, "oldoctinteger" will not be supported, and an exception will be raised if a literal has a leading "0" and a second character which is a digit. For both versions, this will r...
...constructor fails w/ WindowsError: [Errno 6] The handle is invalid since there are no reports of this failing on other flavors of Windows, this looks like to be an ME bug ] Open items -- Need to be resolved before 2.0 final release Decide whether cycle-gc should be enabled by default. Resolve compatibility issues between core xml package and the XML-SIG XML package. Update Tools/compiler so that it is compatible with list comprehensions, import as, and any other new lang...
...constructor would ignore all arguments. This is changed now: the constructor refuses arguments in this case. This might break code that worked under Python 2.2. The simplest fix is to add a no-op __init__: def __init__(self, *args, **kw): pass. Through a bytecode optimizer bug (and I bet you didn't even know Python had a bytecode optimizer :-), "unsigned" hex/oct constants with a leading minus sign would come out with the wrong sign. ("Unsigned" hex/oct constants are those...
...definitions or iterable unpacking. In all these cases, we find that the syntax for sending and that for receiving 'data' are virtually identical. Assignment targets such as variables, attributes and subscripts: foo.bar[2] = foo.bar[3]; Function definitions: a function defined with def foo(x, y, z=6) is called as, e.g., foo(123, y=45), where the actual arguments provided at the call site are matched against the formal parameters at the definition site; Iterable unpacking: a, b = b, a or [a, b] ...
...definition. Other classes don't have a natural ordering of their attributes so you're required to use explicit names in your pattern to match with their attributes. However, it's possible to manually specify the ordering of the attributes allowing positional matching, like in this alternative definition: class Click: __match_args__ = ("position", "button") def __init__(self, pos, btn): self.position = pos self.button = btn ... The __match_args__ special attribut...
...definition section with typing.Sized: from typing import Sized class SupportsClose(Protocol): def close(self) -> None: ... class SizedAndClosable(Sized, SupportsClose, Protocol): pass The two definitions of SizedAndClosable are equivalent. Subclass relationships between protocols are not meaningful when considering subtyping, since structural compatibility is the criterion, not the MRO. If Protocol is included in the base class list, all the other base classes must be prot...
...definition in the nearest enclosing function scope will be used. One consequence of this change is that lambda statements could reference variables in the namespaces where the lambda is defined. In some unusual cases, this change will break code. In all previous version of Python, names were resolved in exactly three namespaces -- the local namespace, the global namespace, and the builtin namespace. According to this old definition, if a function A is defined within a function B, the names bo...