Source code for xonsh.pretty

# -*- coding: utf-8 -*-
"""
Python advanced pretty printer.  This pretty printer is intended to
replace the old `pprint` python module which does not allow developers
to provide their own pretty print callbacks.

This module is based on ruby's `prettyprint.rb` library by `Tanaka Akira`.

The following implementations were forked from the IPython project:
* Copyright (c) 2008-2014, IPython Development Team
* Copyright (C) 2001-2007 Fernando Perez <fperez@colorado.edu>
* Copyright (c) 2001, Janko Hauser <jhauser@zscout.de>
* Copyright (c) 2001, Nathaniel Gray <n8gray@caltech.edu>

Example Usage
-------------

To directly print the representation of an object use `pprint`::

    from pretty import pretty_print
    pretty_pprint(complex_object)

To get a string of the output use `pretty`::

    from pretty import pretty
    string = pretty(complex_object)


Extending
---------

The pretty library allows developers to add pretty printing rules for their
own objects.  This process is straightforward.  All you have to do is to
add a `_repr_pretty_` method to your object and call the methods on the
pretty printer passed::

    class MyObject(object):

        def _repr_pretty_(self, p, cycle):
            ...

Here is an example implementation of a `_repr_pretty_` method for a list
subclass::

    class MyList(list):

        def _repr_pretty_(self, p, cycle):
            if cycle:
                p.text('MyList(...)')
            else:
                with p.group(8, 'MyList([', '])'):
                    for idx, item in enumerate(self):
                        if idx:
                            p.text(',')
                            p.breakable()
                        p.pretty(item)

The `cycle` parameter is `True` if pretty detected a cycle.  You *have* to
react to that or the result is an infinite loop.  `p.text()` just adds
non breaking text to the output, `p.breakable()` either adds a whitespace
or breaks here.  If you pass it an argument it's used instead of the
default space.  `p.pretty` prettyprints another object using the pretty print
method.

The first parameter to the `group` function specifies the extra indentation
of the next line.  In this example the next item will either be on the same
line (if the items are short enough) or aligned with the right edge of the
opening bracket of `MyList`.

If you just want to indent something you can use the group function
without open / close parameters.  You can also use this code::

    with p.indent(2):
        ...


:copyright: 2007 by Armin Ronacher.
            Portions (c) 2009 by Robert Kern.
:license: BSD License.
"""
import io
import re
import sys
import types
import datetime
import contextlib
import collections

from xonsh.lazyasd import LazyObject, lazyobject

__all__ = [
    'pretty', 'pretty_print', 'PrettyPrinter', 'RepresentationPrinter',
    'for_type', 'for_type_by_name']


MAX_SEQ_LENGTH = 1000


def _safe_getattr(obj, attr, default=None):
    """Safe version of getattr.

    Same as getattr, but will return ``default`` on any Exception,
    rather than raising.
    """
    try:
        return getattr(obj, attr, default)
    except Exception:
        return default


CUnicodeIO = io.StringIO


[docs]def pretty(obj, verbose=False, max_width=79, newline='\n', max_seq_length=MAX_SEQ_LENGTH): """ Pretty print the object's representation. """ stream = CUnicodeIO() printer = RepresentationPrinter(stream, verbose, max_width, newline, max_seq_length=max_seq_length) printer.pretty(obj) printer.flush() return stream.getvalue()
[docs]def pretty_print(obj, verbose=False, max_width=79, newline='\n', max_seq_length=MAX_SEQ_LENGTH): """ Like pretty() but print to stdout. """ printer = RepresentationPrinter(sys.stdout, verbose, max_width, newline, max_seq_length=max_seq_length) printer.pretty(obj) printer.flush() sys.stdout.write(newline) sys.stdout.flush()
class _PrettyPrinterBase(object): @contextlib.contextmanager def indent(self, indent): """with statement support for indenting/dedenting.""" self.indentation += indent try: yield finally: self.indentation -= indent @contextlib.contextmanager def group(self, indent=0, open='', close=''): """like begin_group / end_group but for the with statement.""" self.begin_group(indent, open) try: yield finally: self.end_group(indent, close)
[docs]class PrettyPrinter(_PrettyPrinterBase): """ Baseclass for the `RepresentationPrinter` prettyprinter that is used to generate pretty reprs of objects. Contrary to the `RepresentationPrinter` this printer knows nothing about the default pprinters or the `_repr_pretty_` callback method. """ def __init__(self, output, max_width=79, newline='\n', max_seq_length=MAX_SEQ_LENGTH): self.output = output self.max_width = max_width self.newline = newline self.max_seq_length = max_seq_length self.output_width = 0 self.buffer_width = 0 self.buffer = collections.deque() root_group = Group(0) self.group_stack = [root_group] self.group_queue = GroupQueue(root_group) self.indentation = 0 def _break_outer_groups(self): while self.max_width < self.output_width + self.buffer_width: group = self.group_queue.deq() if not group: return while group.breakables: x = self.buffer.popleft() self.output_width = x.output(self.output, self.output_width) self.buffer_width -= x.width while self.buffer and isinstance(self.buffer[0], Text): x = self.buffer.popleft() self.output_width = x.output(self.output, self.output_width) self.buffer_width -= x.width
[docs] def text(self, obj): """Add literal text to the output.""" width = len(obj) if self.buffer: text = self.buffer[-1] if not isinstance(text, Text): text = Text() self.buffer.append(text) text.add(obj, width) self.buffer_width += width self._break_outer_groups() else: self.output.write(obj) self.output_width += width
[docs] def breakable(self, sep=' '): """ Add a breakable separator to the output. This does not mean that it will automatically break here. If no breaking on this position takes place the `sep` is inserted which default to one space. """ width = len(sep) group = self.group_stack[-1] if group.want_break: self.flush() self.output.write(self.newline) self.output.write(' ' * self.indentation) self.output_width = self.indentation self.buffer_width = 0 else: self.buffer.append(Breakable(sep, width, self)) self.buffer_width += width self._break_outer_groups()
[docs] def break_(self): """ Explicitly insert a newline into the output, maintaining correct indentation. """ self.flush() self.output.write(self.newline) self.output.write(' ' * self.indentation) self.output_width = self.indentation self.buffer_width = 0
[docs] def begin_group(self, indent=0, open=''): """ Begin a group. If you want support for python < 2.5 which doesn't has the with statement this is the preferred way: p.begin_group(1, '{') ... p.end_group(1, '}') The python 2.5 expression would be this: with p.group(1, '{', '}'): ... The first parameter specifies the indentation for the next line (usually the width of the opening text), the second the opening text. All parameters are optional. """ if open: self.text(open) group = Group(self.group_stack[-1].depth + 1) self.group_stack.append(group) self.group_queue.enq(group) self.indentation += indent
def _enumerate(self, seq): """like enumerate, but with an upper limit on the number of items""" for idx, x in enumerate(seq): if self.max_seq_length and idx >= self.max_seq_length: self.text(',') self.breakable() self.text('...') return yield idx, x
[docs] def end_group(self, dedent=0, close=''): """End a group. See `begin_group` for more details.""" self.indentation -= dedent group = self.group_stack.pop() if not group.breakables: self.group_queue.remove(group) if close: self.text(close)
[docs] def flush(self): """Flush data that is left in the buffer.""" for data in self.buffer: self.output_width += data.output(self.output, self.output_width) self.buffer.clear() self.buffer_width = 0
def _get_mro(obj_class): """ Get a reasonable method resolution order of a class and its superclasses for both old-style and new-style classes. """ if not hasattr(obj_class, '__mro__'): # Old-style class. Mix in object to make a fake new-style class. try: obj_class = type(obj_class.__name__, (obj_class, object), {}) except TypeError: # Old-style extension type that does not descend from object. # FIXME: try to construct a more thorough MRO. mro = [obj_class] else: mro = obj_class.__mro__[1:-1] else: mro = obj_class.__mro__ return mro
[docs]class RepresentationPrinter(PrettyPrinter): """ Special pretty printer that has a `pretty` method that calls the pretty printer for a python object. This class stores processing data on `self` so you must *never* use this class in a threaded environment. Always lock it or reinstanciate it. Instances also have a verbose flag callbacks can access to control their output. For example the default instance repr prints all attributes and methods that are not prefixed by an underscore if the printer is in verbose mode. """ def __init__(self, output, verbose=False, max_width=79, newline='\n', singleton_pprinters=None, type_pprinters=None, deferred_pprinters=None, max_seq_length=MAX_SEQ_LENGTH): PrettyPrinter.__init__(self, output, max_width, newline, max_seq_length=max_seq_length) self.verbose = verbose self.stack = [] if singleton_pprinters is None: singleton_pprinters = _singleton_pprinters.copy() self.singleton_pprinters = singleton_pprinters if type_pprinters is None: type_pprinters = _type_pprinters.copy() self.type_pprinters = type_pprinters if deferred_pprinters is None: deferred_pprinters = _deferred_type_pprinters.copy() self.deferred_pprinters = deferred_pprinters
[docs] def pretty(self, obj): """Pretty print the given object.""" obj_id = id(obj) cycle = obj_id in self.stack self.stack.append(obj_id) self.begin_group() try: obj_class = _safe_getattr(obj, '__class__', None) or type(obj) # First try to find registered singleton printers for the type. try: printer = self.singleton_pprinters[obj_id] except (TypeError, KeyError): pass else: return printer(obj, self, cycle) # Next walk the mro and check for either: # 1) a registered printer # 2) a _repr_pretty_ method for cls in _get_mro(obj_class): if cls in self.type_pprinters: # printer registered in self.type_pprinters return self.type_pprinters[cls](obj, self, cycle) else: # deferred printer printer = self._in_deferred_types(cls) if printer is not None: return printer(obj, self, cycle) else: # Finally look for special method names. # Some objects automatically create any requested # attribute. Try to ignore most of them by checking for # callability. if '_repr_pretty_' in cls.__dict__: meth = cls._repr_pretty_ if callable(meth): return meth(obj, self, cycle) return _default_pprint(obj, self, cycle) finally: self.end_group() self.stack.pop()
def _in_deferred_types(self, cls): """ Check if the given class is specified in the deferred type registry. Returns the printer from the registry if it exists, and None if the class is not in the registry. Successful matches will be moved to the regular type registry for future use. """ mod = _safe_getattr(cls, '__module__', None) name = _safe_getattr(cls, '__name__', None) key = (mod, name) printer = None if key in self.deferred_pprinters: # Move the printer over to the regular registry. printer = self.deferred_pprinters.pop(key) self.type_pprinters[cls] = printer return printer
class Printable(object): def output(self, stream, output_width): return output_width class Text(Printable): def __init__(self): self.objs = [] self.width = 0 def output(self, stream, output_width): for obj in self.objs: stream.write(obj) return output_width + self.width def add(self, obj, width): self.objs.append(obj) self.width += width class Breakable(Printable): def __init__(self, seq, width, pretty): self.obj = seq self.width = width self.pretty = pretty self.indentation = pretty.indentation self.group = pretty.group_stack[-1] self.group.breakables.append(self) def output(self, stream, output_width): self.group.breakables.popleft() if self.group.want_break: stream.write(self.pretty.newline) stream.write(' ' * self.indentation) return self.indentation if not self.group.breakables: self.pretty.group_queue.remove(self.group) stream.write(self.obj) return output_width + self.width class Group(Printable): def __init__(self, depth): self.depth = depth self.breakables = collections.deque() self.want_break = False class GroupQueue(object): def __init__(self, *groups): self.queue = [] for group in groups: self.enq(group) def enq(self, group): depth = group.depth while depth > len(self.queue) - 1: self.queue.append([]) self.queue[depth].append(group) def deq(self): for stack in self.queue: for idx, group in enumerate(reversed(stack)): if group.breakables: del stack[idx] group.want_break = True return group for group in stack: group.want_break = True del stack[:] def remove(self, group): try: self.queue[group.depth].remove(group) except ValueError: pass @lazyobject def _baseclass_reprs(): try: br = (object.__repr__, types.InstanceType.__repr__) except AttributeError: # Python 3 br = (object.__repr__,) return br def _default_pprint(obj, p, cycle): """ The default print function. Used if an object does not provide one and it's none of the builtin objects. """ klass = _safe_getattr(obj, '__class__', None) or type(obj) if _safe_getattr(klass, '__repr__', None) not in _baseclass_reprs: # A user-provided repr. Find newlines and replace them with p.break_() _repr_pprint(obj, p, cycle) return p.begin_group(1, '<') p.pretty(klass) p.text(' at 0x%x' % id(obj)) if cycle: p.text(' ...') elif p.verbose: first = True for key in dir(obj): if not key.startswith('_'): try: value = getattr(obj, key) except AttributeError: continue if isinstance(value, types.MethodType): continue if not first: p.text(',') p.breakable() p.text(key) p.text('=') step = len(key) + 1 p.indentation += step p.pretty(value) p.indentation -= step first = False p.end_group(1, '>') def _seq_pprinter_factory(start, end, basetype): """ Factory that returns a pprint function useful for sequences. Used by the default pprint for tuples, dicts, and lists. """ def inner(obj, p, cycle): typ = type(obj) if basetype is not None and typ is not basetype and typ.__repr__ != basetype.__repr__: # If the subclass provides its own repr, use it instead. return p.text(typ.__repr__(obj)) if cycle: return p.text(start + '...' + end) step = len(start) p.begin_group(step, start) for idx, x in p._enumerate(obj): if idx: p.text(',') p.breakable() p.pretty(x) if len(obj) == 1 and type(obj) is tuple: # Special case for 1-item tuples. p.text(',') p.end_group(step, end) return inner def _set_pprinter_factory(start, end, basetype): """ Factory that returns a pprint function useful for sets and frozensets. """ def inner(obj, p, cycle): typ = type(obj) if basetype is not None and typ is not basetype and typ.__repr__ != basetype.__repr__: # If the subclass provides its own repr, use it instead. return p.text(typ.__repr__(obj)) if cycle: return p.text(start + '...' + end) if len(obj) == 0: # Special case. p.text(basetype.__name__ + '()') else: step = len(start) p.begin_group(step, start) # Like dictionary keys, we will try to sort the items if there aren't too many items = obj if not (p.max_seq_length and len(obj) >= p.max_seq_length): try: items = sorted(obj) except Exception: # Sometimes the items don't sort. pass for idx, x in p._enumerate(items): if idx: p.text(',') p.breakable() p.pretty(x) p.end_group(step, end) return inner def _dict_pprinter_factory(start, end, basetype=None): """ Factory that returns a pprint function used by the default pprint of dicts and dict proxies. """ def inner(obj, p, cycle): typ = type(obj) if basetype is not None and typ is not basetype and typ.__repr__ != basetype.__repr__: # If the subclass provides its own repr, use it instead. return p.text(typ.__repr__(obj)) if cycle: return p.text('{...}') p.begin_group(1, start) keys = obj.keys() # if dict isn't large enough to be truncated, sort keys before displaying if not (p.max_seq_length and len(obj) >= p.max_seq_length): try: keys = sorted(keys) except Exception: # Sometimes the keys don't sort. pass for idx, key in p._enumerate(keys): if idx: p.text(',') p.breakable() p.pretty(key) p.text(': ') p.pretty(obj[key]) p.end_group(1, end) return inner def _super_pprint(obj, p, cycle): """The pprint for the super type.""" p.begin_group(8, '<super: ') p.pretty(obj.__thisclass__) p.text(',') p.breakable() p.pretty(obj.__self__) p.end_group(8, '>') def _re_pattern_pprint(obj, p, cycle): """The pprint function for regular expression patterns.""" p.text('re.compile(') pattern = repr(obj.pattern) if pattern[:1] in 'uU': pattern = pattern[1:] prefix = 'ur' else: prefix = 'r' pattern = prefix + pattern.replace('\\\\', '\\') p.text(pattern) if obj.flags: p.text(',') p.breakable() done_one = False for flag in ('TEMPLATE', 'IGNORECASE', 'LOCALE', 'MULTILINE', 'DOTALL', 'UNICODE', 'VERBOSE', 'DEBUG'): if obj.flags & getattr(re, flag): if done_one: p.text('|') p.text('re.' + flag) done_one = True p.text(')') def _type_pprint(obj, p, cycle): """The pprint for classes and types.""" # Heap allocated types might not have the module attribute, # and others may set it to None. # Checks for a __repr__ override in the metaclass if type(obj).__repr__ is not type.__repr__: _repr_pprint(obj, p, cycle) return mod = _safe_getattr(obj, '__module__', None) try: name = obj.__qualname__ if not isinstance(name, str): # This can happen if the type implements __qualname__ as a property # or other descriptor in Python 2. raise Exception("Try __name__") except Exception: name = obj.__name__ if not isinstance(name, str): name = '<unknown type>' if mod in (None, '__builtin__', 'builtins', 'exceptions'): p.text(name) else: p.text(mod + '.' + name) def _repr_pprint(obj, p, cycle): """A pprint that just redirects to the normal repr function.""" # Find newlines and replace them with p.break_() output = repr(obj) for idx, output_line in enumerate(output.splitlines()): if idx: p.break_() p.text(output_line) def _function_pprint(obj, p, cycle): """Base pprint for all functions and builtin functions.""" name = _safe_getattr(obj, '__qualname__', obj.__name__) mod = obj.__module__ if mod and mod not in ('__builtin__', 'builtins', 'exceptions'): name = mod + '.' + name p.text('<function %s>' % name) def _exception_pprint(obj, p, cycle): """Base pprint for all exceptions.""" name = getattr(obj.__class__, '__qualname__', obj.__class__.__name__) if obj.__class__.__module__ not in ('exceptions', 'builtins'): name = '%s.%s' % (obj.__class__.__module__, name) step = len(name) + 1 p.begin_group(step, name + '(') for idx, arg in enumerate(getattr(obj, 'args', ())): if idx: p.text(',') p.breakable() p.pretty(arg) p.end_group(step, ')') @lazyobject def _type_pprinters(): #: printers for builtin types tp = { int: _repr_pprint, float: _repr_pprint, str: _repr_pprint, tuple: _seq_pprinter_factory('(', ')', tuple), list: _seq_pprinter_factory('[', ']', list), dict: _dict_pprinter_factory('{', '}', dict), set: _set_pprinter_factory('{', '}', set), frozenset: _set_pprinter_factory('frozenset({', '})', frozenset), super: _super_pprint, type(re.compile('')): _re_pattern_pprint, type: _type_pprint, types.FunctionType: _function_pprint, types.BuiltinFunctionType: _function_pprint, types.MethodType: _repr_pprint, datetime.datetime: _repr_pprint, datetime.timedelta: _repr_pprint, } #: the exception base try: _exception_base = BaseException except NameError: _exception_base = Exception tp[_exception_base] = _exception_pprint try: tp[types.DictProxyType] = _dict_pprinter_factory('<dictproxy {', '}>') tp[types.ClassType] = _type_pprint tp[types.SliceType] = _repr_pprint except AttributeError: # Python 3 tp[slice] = _repr_pprint try: tp[xrange] = _repr_pprint tp[long] = _repr_pprint tp[unicode] = _repr_pprint except NameError: tp[range] = _repr_pprint tp[bytes] = _repr_pprint return tp #: printers for types specified by name @lazyobject def _deferred_type_pprinters(): dtp = {} for_type_by_name('collections', 'defaultdict', _defaultdict_pprint, dtp=dtp) for_type_by_name('collections', 'OrderedDict', _ordereddict_pprint, dtp=dtp) for_type_by_name('collections', 'deque', _deque_pprint, dtp=dtp) for_type_by_name('collections', 'Counter', _counter_pprint, dtp=dtp) return dtp
[docs]def for_type(typ, func): """ Add a pretty printer for a given type. """ oldfunc = _type_pprinters.get(typ, None) if func is not None: # To support easy restoration of old pprinters, we need to ignore Nones. _type_pprinters[typ] = func return oldfunc
[docs]def for_type_by_name(type_module, type_name, func, dtp=None): """ Add a pretty printer for a type specified by the module and name of a type rather than the type object itself. """ if dtp is None: dtp = _deferred_type_pprinters key = (type_module, type_name) oldfunc = dtp.get(key, None) if func is not None: # To support easy restoration of old pprinters, we need to ignore Nones. dtp[key] = func return oldfunc
#: printers for the default singletons _singleton_pprinters = LazyObject(lambda: dict.fromkeys( map(id, [None, True, False, Ellipsis, NotImplemented]), _repr_pprint), globals(), '_singleton_pprinters') def _defaultdict_pprint(obj, p, cycle): name = obj.__class__.__name__ with p.group(len(name) + 1, name + '(', ')'): if cycle: p.text('...') else: p.pretty(obj.default_factory) p.text(',') p.breakable() p.pretty(dict(obj)) def _ordereddict_pprint(obj, p, cycle): name = obj.__class__.__name__ with p.group(len(name) + 1, name + '(', ')'): if cycle: p.text('...') elif len(obj): p.pretty(list(obj.items())) def _deque_pprint(obj, p, cycle): name = obj.__class__.__name__ with p.group(len(name) + 1, name + '(', ')'): if cycle: p.text('...') else: p.pretty(list(obj)) def _counter_pprint(obj, p, cycle): name = obj.__class__.__name__ with p.group(len(name) + 1, name + '(', ')'): if cycle: p.text('...') elif len(obj): p.pretty(dict(obj))