144 lines
4.4 KiB
Python
144 lines
4.4 KiB
Python
# pprint.py
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#
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# Author: Fred L. Drake, Jr.
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# fdrake@vt.edu
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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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#
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"""Support to pretty-print lists, tuples, & dictionaries recursively.
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Very simple, but at least somewhat useful, especially in debugging
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data structures.
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INDENT_PER_LEVEL -- Amount of indentation to use for each new
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recursive level. The default is 1. This
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must be a non-negative integer, and may be
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set by the caller before calling pprint().
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MAX_WIDTH -- Maximum width of the display. This is only
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used if the representation *can* be kept
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less than MAX_WIDTH characters wide. May
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be set by the user before calling pprint().
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TAB_WIDTH -- The width represented by a single tab. This
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value is typically 8, but 4 is the default
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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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pprint(seq [, stream]) -- The pretty-printer. This takes a Python
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object (presumably a sequence, but that
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doesn't matter) and an optional output
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stream. See the function documentation
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for details.
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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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def _indentation(cols):
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"Create tabbed indentation string COLS columns wide."
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# This is used to reduce the byte-count for the output, allowing
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# files created using this module to use as little external storage
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# as possible. This is primarily intended to minimize impact on
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# a user's quota when storing resource files, or for creating output
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# intended for transmission.
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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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pprint(seq [, stream]) ==> None
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If STREAM is provided, output is written to that stream, otherwise
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sys.stdout is used. Indentation is done according to
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INDENT_PER_LEVEL, which may be set to any non-negative integer
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before calling this function. The output written on the stream is
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a perfectly valid representation of the Python object passed in,
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with indentation to suite human-readable interpretation. The
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output can be used as input without error, given readable
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representations of all sequence elements are available via repr().
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Output is restricted to MAX_WIDTH columns where possible. The
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STREAM parameter must support the write() method with a single
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parameter, which will always be a string. The output stream may be
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a StringIO.StringIO object if the result is needed as a string.
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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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from types import DictType, ListType, TupleType
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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 pprint.py
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