def demo():
"""
A demonstration of the recursive descent parser.
"""
from nltk import parse, cfg
grammar = cfg.parse_cfg("""
S -> NP VP
NP -> Det N | Det N PP
VP -> V NP | V NP PP
PP -> P NP
NP -> 'I'
N -> 'man' | 'park' | 'telescope' | 'dog'
Det -> 'the' | 'a'
P -> 'in' | 'with'
V -> 'saw'
""")
for prod in grammar.productions():
print prod
sent = 'I saw a man in the park'.split()
parser = parse.RecursiveDescentParser(grammar, trace=2)
for p in parser.nbest_parse(sent):
print p
def demo():
from nltk import cfg
nonterminals = 'S VP NP PP P N Name V Det'
(S, VP, NP, PP, P, N, Name, V, Det) = [cfg.Nonterminal(s)
for s in nonterminals.split()]
grammar = cfg.parse_cfg("""
S -> NP VP
PP -> P NP
NP -> Det N
NP -> NP PP
VP -> V NP
VP -> VP PP
Det -> 'a'
Det -> 'the'
Det -> 'my'
NP -> 'I'
N -> 'dog'
N -> 'man'
N -> 'park'
N -> 'statue'
V -> 'saw'
P -> 'in'
P -> 'up'
P -> 'over'
P -> 'with'
""")
def cb(grammar): print grammar
top = Tk()
editor = CFGEditor(top, grammar, cb)
Label(top, text='\nTesting CFG Editor\n').pack()
Button(top, text='Quit', command=top.destroy).pack()
top.mainloop()
def cfg_demo():
"""
A demonstration showing how C{Grammar}s can be created and used.
"""
from nltk import cfg
# Create some nonterminals
S, NP, VP, PP = cfg.nonterminals('S, NP, VP, PP')
N, V, P, Det = cfg.nonterminals('N, V, P, Det')
VP_slash_NP = VP/NP
print 'Some nonterminals:', [S, NP, VP, PP, N, V, P, Det, VP/NP]
print ' S.symbol() =>', `S.symbol()`
print
print cfg.Production(S, [NP])
# Create some Grammar Productions
grammar = cfg.parse_cfg("""
S -> NP VP
PP -> P NP
NP -> Det N | NP PP
VP -> V NP | VP PP
Det -> 'a' | 'the'
N -> 'dog' | 'cat'
V -> 'chased' | 'sat'
P -> 'on' | 'in'
""")
print 'A Grammar:', `grammar`
print ' grammar.start() =>', `grammar.start()`
print ' grammar.productions() =>',
# Use string.replace(...) is to line-wrap the output.
print `grammar.productions()`.replace(',', ',\n'+' '*25)
print
print 'Coverage of input words by a grammar:'
print grammar.covers(['a','dog'])
print grammar.covers(['a','toy'])
def cfg_demo():
"""
A demonstration showing how C{Grammar}s can be created and used.
"""
from nltk import cfg
# Create some nonterminals
S, NP, VP, PP = cfg.nonterminals('S, NP, VP, PP')
N, V, P, Det = cfg.nonterminals('N, V, P, Det')
VP_slash_NP = VP / NP
print 'Some nonterminals:', [S, NP, VP, PP, N, V, P, Det, VP / NP]
print ' S.symbol() =>', ` S.symbol() `
print
print cfg.Production(S, [NP])
# Create some Grammar Productions
grammar = cfg.parse_cfg("""
S -> NP VP
PP -> P NP
NP -> Det N | NP PP
VP -> V NP | VP PP
Det -> 'a' | 'the'
N -> 'dog' | 'cat'
V -> 'chased' | 'sat'
P -> 'on' | 'in'
""")
print 'A Grammar:', ` grammar `
print ' grammar.start() =>', ` grammar.start() `
print ' grammar.productions() =>',
# Use string.replace(...) is to line-wrap the output.
print ` grammar.productions() `.replace(',', ',\n' + ' ' * 25)
print
print 'Coverage of input words by a grammar:'
print grammar.covers(['a', 'dog'])
print grammar.covers(['a', 'toy'])
def demo():
"""
A demonstration of the shift-reduce parser.
"""
from nltk import parse, cfg
grammar = cfg.parse_cfg("""
S -> NP VP
NP -> Det N | Det N PP
VP -> V NP | V NP PP
PP -> P NP
NP -> 'I'
N -> 'man' | 'park' | 'telescope' | 'dog'
Det -> 'the' | 'a'
P -> 'in' | 'with'
V -> 'saw'
""")
sent = 'I saw a man in the park'.split()
parser = parse.ShiftReduceParser(grammar, trace=2)
for p in parser.nbest_parse(sent):
print p
def demo():
"""
A demonstration of the shift-reduce parser.
"""
from nltk import parse, cfg
grammar = cfg.parse_cfg("""
S -> NP VP
NP -> Det N | Det N PP
VP -> V NP | V NP PP
PP -> P NP
NP -> 'I'
N -> 'man' | 'park' | 'telescope' | 'dog'
Det -> 'the' | 'a'
P -> 'in' | 'with'
V -> 'saw'
""")
sent = 'I saw a man in the park'.split()
parser = parse.ShiftReduceParser(grammar, trace=2)
for p in parser.nbest_parse(sent):
print p
def load(resource_url, format='auto', cache=True, verbose=False):
"""
Load a given resource from the NLTK data package. The following
resource formats are currently supported:
- C{'pickle'}
- C{'yaml'}
- C{'cfg'} (context free grammars)
- C{'pcfg'} (probabilistic CFGs)
- C{'fcfg'} (feature-based CFGs)
- C{'fol'} (formulas of First Order Logic)
- C{'val'} (valuation of First Order Logic model)
- C{'raw'}
If no format is specified, C{load()} will attempt to determine a
format based on the resource name's file extension. If that
fails, C{load()} will raise a C{ValueError} exception.
@type resource_url: C{str}
@param resource_url: A URL specifying where the resource should be
loaded from. The default protocol is C{"nltk:"}, which searches
for the file in the the NLTK data package.
@type cache: C{bool}
@param cache: If true, add this resource to a cache. If C{load}
finds a resource in its cache, then it will return it from the
cache rather than loading it. The cache uses weak references,
so a resource wil automatically be expunged from the cache
when no more objects are using it.
@type verbose: C{bool}
@param verbose: If true, print a message when loading a resource.
Messages are not displayed when a resource is retrieved from
the cache.
"""
# If we've cached the resource, then just return it.
if cache:
resource_val = _resource_cache.get(resource_url)
if resource_val is not None:
if verbose:
print '<<Using cached copy of %s>>' % (resource_url,)
return resource_val
# Let the user know what's going on.
if verbose:
print '<<Loading %s>>' % (resource_url,)
# Determine the format of the resource.
if format == 'auto':
if resource_url.endswith('.pickle'): format = 'pickle'
if resource_url.endswith('.yaml'): format = 'yaml'
if resource_url.endswith('.cfg'): format = 'cfg'
if resource_url.endswith('.pcfg'): format = 'pcfg'
if resource_url.endswith('.fcfg'): format = 'fcfg'
if resource_url.endswith('.fol'): format = 'fol'
if resource_url.endswith('.val'): format = 'val'
# Load the resource.
if format == 'pickle':
resource_val = pickle.load(_open(resource_url))
elif format == 'yaml':
resource_val = yaml.load(_open(resource_url))
elif format == 'cfg':
resource_val = cfg.parse_cfg(_open(resource_url).read())
elif format == 'pcfg':
resource_val = cfg.parse_pcfg(_open(resource_url).read())
elif format == 'fcfg':
resource_val = cfg.parse_fcfg(_open(resource_url).read())
elif format == 'fol':
resource_val = sem.parse_fol(_open(resource_url).read())
elif format == 'val':
resource_val = sem.parse_valuation(_open(resource_url).read())
elif format == 'raw':
resource_val = _open(resource_url).read()
else:
raise ValueError('Unknown format type!')
# If requested, add it to the cache.
if cache:
try:
_resource_cache[resource_url] = resource_val
except TypeError:
# We can't create weak references to some object types, like
# strings and tuples. For now, just don't cache them.
pass
return resource_val
for frag2 in _generate_all(grammar, items[1:]):
for frag in _multiply(frag1, frag2):
frags.append(frag)
return frags
def _multiply(frag1, frag2):
frags = []
if len(frag1) == 1:
frag1 = [frag1]
if len(frag2) == 1:
frag2 = [frag2]
for f1 in frag1:
for f2 in frag2:
frags.append(f1+f2)
return frags
grammar = cfg.parse_cfg("""
S -> NP VP
NP -> Det N
VP -> V NP
Det -> 'the'
Det -> 'a'
N -> 'man' | 'park' | 'dog' | 'telescope'
V -> 'saw' | 'walked'
P -> 'in' | 'with'
""")
for sent in generate(grammar):
print sent
for frag in _multiply(frag1, frag2):
frags.append(frag)
return frags
def _multiply(frag1, frag2):
frags = []
if len(frag1) == 1:
frag1 = [frag1]
if len(frag2) == 1:
frag2 = [frag2]
for f1 in frag1:
for f2 in frag2:
frags.append(f1 + f2)
return frags
grammar = cfg.parse_cfg("""
S -> NP VP
NP -> Det N
VP -> V NP
Det -> 'the'
Det -> 'a'
N -> 'man' | 'park' | 'dog' | 'telescope'
V -> 'saw' | 'walked'
P -> 'in' | 'with'
""")
for sent in generate(grammar):
print sent
def load(resource_url, format='auto', cache=True, verbose=False):
"""
Load a given resource from the NLTK data package. The following
resource formats are currently supported:
- C{'pickle'}
- C{'yaml'}
- C{'cfg'} (context free grammars)
- C{'pcfg'} (probabilistic CFGs)
- C{'fcfg'} (feature-based CFGs)
- C{'fol'} (formulas of First Order Logic)
- C{'val'} (valuation of First Order Logic model)
- C{'raw'}
If no format is specified, C{load()} will attempt to determine a
format based on the resource name's file extension. If that
fails, C{load()} will raise a C{ValueError} exception.
@type resource_url: C{str}
@param resource_url: A URL specifying where the resource should be
loaded from. The default protocol is C{"nltk:"}, which searches
for the file in the the NLTK data package.
@type cache: C{bool}
@param cache: If true, add this resource to a cache. If C{load}
finds a resource in its cache, then it will return it from the
cache rather than loading it. The cache uses weak references,
so a resource wil automatically be expunged from the cache
when no more objects are using it.
@type verbose: C{bool}
@param verbose: If true, print a message when loading a resource.
Messages are not displayed when a resource is retrieved from
the cache.
"""
# If we've cached the resource, then just return it.
if cache:
resource_val = _resource_cache.get(resource_url)
if resource_val is not None:
if verbose:
print '<<Using cached copy of %s>>' % (resource_url, )
return resource_val
# Let the user know what's going on.
if verbose:
print '<<Loading %s>>' % (resource_url, )
# Determine the format of the resource.
if format == 'auto':
if resource_url.endswith('.pickle'): format = 'pickle'
if resource_url.endswith('.yaml'): format = 'yaml'
if resource_url.endswith('.cfg'): format = 'cfg'
if resource_url.endswith('.pcfg'): format = 'pcfg'
if resource_url.endswith('.fcfg'): format = 'fcfg'
if resource_url.endswith('.fol'): format = 'fol'
if resource_url.endswith('.val'): format = 'val'
# Load the resource.
if format == 'pickle':
resource_val = pickle.load(_open(resource_url))
elif format == 'yaml':
resource_val = yaml.load(_open(resource_url))
elif format == 'cfg':
resource_val = cfg.parse_cfg(_open(resource_url).read())
elif format == 'pcfg':
resource_val = cfg.parse_pcfg(_open(resource_url).read())
elif format == 'fcfg':
resource_val = cfg.parse_fcfg(_open(resource_url).read())
elif format == 'fol':
resource_val = sem.parse_fol(_open(resource_url).read())
elif format == 'val':
resource_val = sem.parse_valuation(_open(resource_url).read())
elif format == 'raw':
resource_val = _open(resource_url).read()
else:
raise ValueError('Unknown format type!')
# If requested, add it to the cache.
if cache:
try:
_resource_cache[resource_url] = resource_val
except TypeError:
# We can't create weak references to some object types, like
# strings and tuples. For now, just don't cache them.
pass
return resource_val
