cpython/Lib/repr.py

"""Redo the builtin repr() (representation) but with limits on most sizes."""

__all__ = ["Repr","repr"]

import __builtin__
from itertools import islice

class Repr:

    def __init__(self):
        self.maxlevel = 6
        self.maxtuple = 6
        self.maxlist = 6
        self.maxarray = 5
        self.maxdict = 4
        self.maxset = 6
        self.maxfrozenset = 6
        self.maxdeque = 6
        self.maxstring = 30
        self.maxlong = 40
        self.maxother = 20

    def repr(self, x):
        return self.repr1(x, self.maxlevel)

    def repr1(self, x, level):
        typename = type(x).__name__
        if ' ' in typename:
            parts = typename.split()
            typename = '_'.join(parts)
        if hasattr(self, 'repr_' + typename):
            return getattr(self, 'repr_' + typename)(x, level)
        else:
            s = __builtin__.repr(x)
            if len(s) > self.maxother:
                i = max(0, (self.maxother-3)//2)
                j = max(0, self.maxother-3-i)
                s = s[:i] + '...' + s[len(s)-j:]
            return s

    def _repr_iterable(self, x, level, left, right, maxiter, trail=''):
        n = len(x)
        if level <= 0 and n:
            s = '...'
        else:
            newlevel = level - 1
            repr1 = self.repr1
            pieces = [repr1(elem, newlevel) for elem in islice(x, maxiter)]
            if n > maxiter:  pieces.append('...')
            s = ', '.join(pieces)
            if n == 1 and trail:  right = trail + right
        return '%s%s%s' % (left, s, right)

    def repr_tuple(self, x, level):
        return self._repr_iterable(x, level, '(', ')', self.maxtuple, ',')

    def repr_list(self, x, level):
        return self._repr_iterable(x, level, '[', ']', self.maxlist)

    def repr_array(self, x, level):
        header = "array('%s', [" % x.typecode
        return self._repr_iterable(x, level, header, '])', self.maxarray)

    def repr_set(self, x, level):
        x = _possibly_sorted(x)
        return self._repr_iterable(x, level, 'set([', '])', self.maxset)

    def repr_frozenset(self, x, level):
        x = _possibly_sorted(x)
        return self._repr_iterable(x, level, 'frozenset([', '])',
                                   self.maxfrozenset)

    def repr_deque(self, x, level):
        return self._repr_iterable(x, level, 'deque([', '])', self.maxdeque)

    def repr_dict(self, x, level):
        n = len(x)
        if n == 0: return '{}'
        if level <= 0: return '{...}'
        newlevel = level - 1
        repr1 = self.repr1
        pieces = []
        for key in islice(_possibly_sorted(x), self.maxdict):
            keyrepr = repr1(key, newlevel)
            valrepr = repr1(x[key], newlevel)
            pieces.append('%s: %s' % (keyrepr, valrepr))
        if n > self.maxdict: pieces.append('...')
        s = ', '.join(pieces)
        return '{%s}' % (s,)

    def repr_str(self, x, level):
        s = __builtin__.repr(x[:self.maxstring])
        if len(s) > self.maxstring:
            i = max(0, (self.maxstring-3)//2)
            j = max(0, self.maxstring-3-i)
            s = __builtin__.repr(x[:i] + x[len(x)-j:])
            s = s[:i] + '...' + s[len(s)-j:]
        return s

    def repr_long(self, x, level):
        s = __builtin__.repr(x) # XXX Hope this isn't too slow...
        if len(s) > self.maxlong:
            i = max(0, (self.maxlong-3)//2)
            j = max(0, self.maxlong-3-i)
            s = s[:i] + '...' + s[len(s)-j:]
        return s

    def repr_instance(self, x, level):
        try:
            s = __builtin__.repr(x)
            # Bugs in x.__repr__() can cause arbitrary
            # exceptions -- then make up something
        except Exception:
            return '<%s instance at %x>' % (x.__class__.__name__, id(x))
        if len(s) > self.maxstring:
            i = max(0, (self.maxstring-3)//2)
            j = max(0, self.maxstring-3-i)
            s = s[:i] + '...' + s[len(s)-j:]
        return s


def _possibly_sorted(x):
    # Since not all sequences of items can be sorted and comparison
    # functions may raise arbitrary exceptions, return an unsorted
    # sequence in that case.
    try:
        return sorted(x)
    except Exception:
        return list(x)

aRepr = Repr()
repr = aRepr.repr