mirror of https://github.com/python/cpython
137 lines
3.9 KiB
Python
137 lines
3.9 KiB
Python
# pprint.py
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#
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# Author: Fred L. Drake, Jr.
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# fdrake@cnri.reston.va.us, fdrake@intr.net
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#
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# This is a simple little module I wrote to make life easier. I didn't
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# see anything quite like it in the library, though I may have overlooked
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# something. I wrote this when I was trying to read some heavily nested
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# tuples with fairly non-descriptive content. This is modelled very much
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# after Lisp/Scheme - style pretty-printing of lists. If you find it
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# useful, thank small children who sleep at night.
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"""Support to pretty-print lists, tuples, & dictionaries recursively.
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Very simple, but useful, especially in debugging data structures.
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Constants
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---------
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INDENT_PER_LEVEL
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Amount of indentation to use for each new recursive level. The
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default is 1. This must be a non-negative integer, and may be set
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by the caller before calling pprint().
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MAX_WIDTH
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Maximum width of the display. This is only used if the
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representation *can* be kept less than MAX_WIDTH characters wide.
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May be set by the user before calling pprint().
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TAB_WIDTH
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The width represented by a single tab. This value is typically 8,
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but 4 is the default under MacOS. Can be changed by the user if
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desired, but is probably not a good idea.
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"""
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INDENT_PER_LEVEL = 1
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MAX_WIDTH = 80
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import os
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TAB_WIDTH = (os.name == 'mac' and 4) or 8
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del os
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from types import DictType, ListType, TupleType
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def _indentation(cols):
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"""Create tabbed indentation string.
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cols
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Width of the indentation, in columns.
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"""
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return ((cols / TAB_WIDTH) * '\t') + ((cols % TAB_WIDTH) * ' ')
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def pprint(seq, stream = None, indent = 0, allowance = 0):
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"""Pretty-print a list, tuple, or dictionary.
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seq
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List, tuple, or dictionary object to be pretty-printed. Other
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object types are permitted by are not specially interpreted.
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stream
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Output stream. If not provided, `sys.stdout' is used. This
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parameter must support the `write()' method with a single
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parameter, which will always be a string. It may be a
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`StringIO.StringIO' object if the result is needed as a
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string.
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Indentation is done according to `INDENT_PER_LEVEL', which may be
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set to any non-negative integer before calling this function. The
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output written on the stream is a perfectly valid representation
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of the Python object passed in, with indentation to assist
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human-readable interpretation. The output can be used as input
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without error, given readable representations of all elements are
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available via `repr()'. Output is restricted to `MAX_WIDTH'
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columns where possible.
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"""
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if stream is None:
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import sys
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stream = sys.stdout
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rep = `seq`
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typ = type(seq)
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sepLines = len(rep) > (MAX_WIDTH - 1 - indent - allowance)
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if sepLines and (typ is ListType or typ is TupleType):
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# Pretty-print the sequence.
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stream.write(((typ is ListType) and '[') or '(')
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length = len(seq)
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if length:
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indent = indent + INDENT_PER_LEVEL
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pprint(seq[0], stream, indent, allowance + 1)
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if len(seq) > 1:
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for ent in seq[1:]:
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stream.write(',\n' + _indentation(indent))
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pprint(ent, stream, indent, allowance + 1)
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indent = indent - INDENT_PER_LEVEL
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stream.write(((typ is ListType) and ']') or ')')
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elif typ is DictType and sepLines:
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stream.write('{')
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length = len(seq)
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if length:
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indent = indent + INDENT_PER_LEVEL
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items = seq.items()
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items.sort()
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key, ent = items[0]
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rep = `key` + ': '
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stream.write(rep)
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pprint(ent, stream, indent + len(rep), allowance + 1)
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if len(items) > 1:
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for key, ent in items[1:]:
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rep = `key` + ': '
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stream.write(',\n' + _indentation(indent) + rep)
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pprint(ent, stream, indent + len(rep), allowance + 1)
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indent = indent - INDENT_PER_LEVEL
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stream.write('}')
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else:
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stream.write(rep)
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# Terminate the 'print' if we're not a recursive invocation.
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if not indent:
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stream.write('\n')
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#
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# end of file
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