Re: [Tutor] test
Hi guys I'll be happy if someone can help evaluate the result of this statement: for n in range (3, 20): > for x in range (2, n): > print (n) > I tried but couldn't figure out why the loop returned such a result Merry Christmas Thanks ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] test
Il 27/12/2010 14.44, Chrystal ha scritto: > Hi guys > > I'll be happy if someone can help evaluate the result of this statement: > > for n in range (3, 20): > for x in range (2, n): > print (n) > > > I tried but couldn't figure out why the loop returned such a result > > Merry Christmas > > Thanks > > What result is so strange for you? I get a perfectly understandable 3 4 4 5 5 5 6 6 6 6 7 7 7 7 7 ... And so on up to 19 repeated 17 times... cheers paolino ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] test
Chrystal wrote:
Hi guys
I'll be happy if someone can help evaluate the result of this statement:
for n in range (3, 20):
for x in range (2, n):
print (n)
I tried but couldn't figure out why the loop returned such a result
It would help if you told us what result you get, what result you
expected, and what you don't understand about it.
My guess is that you expected it to print:
2
2
3
2
3
4
2
3
4
5
...
but instead it prints:
2
3
3
4
4
4
5
5
5
5
...
Hint: you are print n each time, not x. n doesn't vary inside the inner
loop, only in the outer loop.
To understand what is going on better, it might help if you run this
instead:
for n in range(3, 20):
for x in range(2, n):
print('n = %d, x = %d' % (n, x))
--
Steven
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[Tutor] Python 2.7.1 interpreter complains about NameError: global name 'levenshtein_automata' is not defined
Good morning, I am using Python 2.7.1 on Windows XP Service Pack 3. Here
is the program where the Python interpreter complains about NameError:
global name 'levenshtein_automata' is not defined.
The python 2,7.1 error message is:
Traceback (most recent call last):
File "automata_test.py", line 174, in
length = len(list(testdfa.find_all_matches('food', 1, m)))
File "automata_test.py", line 145, in find_all_matches
lev = levenshtein_automata(word, k).to_dfa()
NameError: global name 'levenshtein_automata' is not defined
Here is the program. I have marked lines 174, 145 and 125.
import bisect
import random
class NFA(object):
EPSILON = object()
ANY = object()
def __init__(self, start_state):
self.transitions = {}
self.final_states = set()
self._start_state = start_state
@property
def start_state(self):
return frozenset(self._expand(set([self._start_state])))
def add_transition(self, src, input, dest):
self.transitions.setdefault(src, {}).setdefault(input, set()).add(dest)
def add_final_state(self, state):
self.final_states.add(state)
def is_final(self, states):
return self.final_states.intersection(states)
def _expand(self, states):
frontier = set(states)
while frontier:
state = frontier.pop()
new_states = self.transitions.get(state, {}).get(NFA.EPSILON,
set()).difference(states)
frontier.update(new_states)
states.update(new_states)
return states
def next_state(self, states, input):
dest_states = set()
for state in states:
state_transitions = self.transitions.get(state, {})
dest_states.update(state_transitions.get(input, []))
dest_states.update(state_transitions.get(NFA.ANY, []))
return frozenset(self._expand(dest_states))
def get_inputs(self, states):
inputs = set()
for state in states:
inputs.update(self.transitions.get(state, {}).keys())
return inputs
def to_dfa(self):
dfa = DFA(self.start_state)
frontier = [self.start_state]
seen = set()
while frontier:
current = frontier.pop()
inputs = self.get_inputs(current)
for input in inputs:
if input == NFA.EPSILON: continue
new_state = self.next_state(current, input)
if new_state not in seen:
frontier.append(new_state)
seen.add(new_state)
if self.is_final(new_state):
dfa.add_final_state(new_state)
if input == NFA.ANY:
dfa.set_default_transition(current, new_state)
else:
dfa.add_transition(current, input, new_state)
return dfa
class DFA(object):
def __init__(self, start_state):
self.start_state = start_state
self.transitions = {}
self.defaults = {}
self.final_states = set()
def add_transition(self, src, input, dest):
self.transitions.setdefault(src, {})[input] = dest
def set_default_transition(self, src, dest):
self.defaults[src] = dest
def add_final_state(self, state):
self.final_states.add(state)
def is_final(self, state):
return state in self.final_states
def next_state(self, src, input):
state_transitions = self.transitions.get(src, {})
return state_transitions.get(input, self.defaults.get(src, None))
def next_valid_string(self, input):
state = self.start_state
stack = []
# Evaluate the DFA as far as possible
print state
for i, x in enumerate(input):
print "%s" % input
print 'e'
stack.append((input[:i], state, x))
state = self.next_state(state, x)
if not state: break
else:
stack.append((input[:i+1], state, None))
if self.is_final(state):
# Input word is already valid
return input
# Perform a 'wall following' search for the lexicographically
smallest
# accepting state.
while stack:
path, state, x = stack.pop()
x = self.find_next_edge(state, x)
#print 'x'
if x:
path += x
state = self.next_state(state, x)
if self.is_final(state):
print 'p'
return path
stack.append((path, state, None))
print 'v'
return None
def find_next_edge(self, s, x):
if x is None:
x = '\0' # u'\0'
else:
x = chr(ord(x) + 1)
state_transitions = self.transitions.get(s, {})
if x in state_transitions or s in self.defaults:
return x
labels = sorted(state_transitions.keys())
pos = bisect.bisect_left(labels, x)
if pos < len(labels):
print 'n'
return labels[pos]
return None
def levenshtein_automata(self, term, k):# line 125 '
nfa = NFA((0, 0))
for i, c in enumerate(term):
for e in range(k + 1):
# Correct character
nfa.add_transition((i, e), c, (i + 1, e))
if e < k:
# Deletion
nfa.add_transition((i, e), NFA.ANY, (i, e + 1))
# Insertion
nfa.add_transition((i, e), NFA.EPSILON, (i + 1, e + 1))
# Substitution
nfa.add_transition((i, e), NFA.ANY, (i + 1, e + 1))
Re: [Tutor] Python 2.7.1 interpreter complains about NameError: global name 'levenshtein_automata' is not defined
It appears that you've defined "levenshtein_automata" as a method on your DFA class, but you did not reference the class instance in your call by prefixing "self". Instead, you're trying to call a globally defined function named "levenshtein_automata" -- which because it is not defined, is throwing a NameError. Try changing line 145 to the below and see if that resolves the issue: lev = self.levenshtein_automata(word, k).to_dfa() # line 145 ## ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Python 2.7.1 interpreter complains about NameError: global name 'levenshtein_automata' is not defined
See my comment following line 145:
On 12/27/2010 8:25 PM, Frank Chang wrote:
Good morning, I am using Python 2.7.1 on Windows XP Service Pack 3.
Here is the program where the Python interpreter complains about
NameError: global name 'levenshtein_automata' is not defined.
The python 2,7.1 error message is:
Traceback (most recent call last):
File "automata_test.py", line 174, in
length = len(list(testdfa.find_all_matches('food', 1, m)))
File "automata_test.py", line 145, in find_all_matches
lev = levenshtein_automata(word, k).to_dfa()
NameError: global name 'levenshtein_automata' is not defined
Here is the program. I have marked lines 174, 145 and 125.
import bisect
import random
class NFA(object):
EPSILON = object()
ANY = object()
def __init__(self, start_state):
self.transitions = {}
self.final_states = set()
self._start_state = start_state
@property
def start_state(self):
return frozenset(self._expand(set([self._start_state])))
def add_transition(self, src, input, dest):
self.transitions.setdefault(src, {}).setdefault(input,
set()).add(dest)
def add_final_state(self, state):
self.final_states.add(state)
def is_final(self, states):
return self.final_states.intersection(states)
def _expand(self, states):
frontier = set(states)
while frontier:
state = frontier.pop()
new_states = self.transitions.get(state, {}).get(NFA.EPSILON,
set()).difference(states)
frontier.update(new_states)
states.update(new_states)
return states
def next_state(self, states, input):
dest_states = set()
for state in states:
state_transitions = self.transitions.get(state, {})
dest_states.update(state_transitions.get(input, []))
dest_states.update(state_transitions.get(NFA.ANY, []))
return frozenset(self._expand(dest_states))
def get_inputs(self, states):
inputs = set()
for state in states:
inputs.update(self.transitions.get(state, {}).keys())
return inputs
def to_dfa(self):
dfa = DFA(self.start_state)
frontier = [self.start_state]
seen = set()
while frontier:
current = frontier.pop()
inputs = self.get_inputs(current)
for input in inputs:
if input == NFA.EPSILON: continue
new_state = self.next_state(current, input)
if new_state not in seen:
frontier.append(new_state)
seen.add(new_state)
if self.is_final(new_state):
dfa.add_final_state(new_state)
if input == NFA.ANY:
dfa.set_default_transition(current, new_state)
else:
dfa.add_transition(current, input, new_state)
return dfa
class DFA(object):
def __init__(self, start_state):
self.start_state = start_state
self.transitions = {}
self.defaults = {}
self.final_states = set()
def add_transition(self, src, input, dest):
self.transitions.setdefault(src, {})[input] = dest
def set_default_transition(self, src, dest):
self.defaults[src] = dest
def add_final_state(self, state):
self.final_states.add(state)
def is_final(self, state):
return state in self.final_states
def next_state(self, src, input):
state_transitions = self.transitions.get(src, {})
return state_transitions.get(input, self.defaults.get(src, None))
def next_valid_string(self, input):
state = self.start_state
stack = []
# Evaluate the DFA as far as possible
print state
for i, x in enumerate(input):
print "%s" % input
print 'e'
stack.append((input[:i], state, x))
state = self.next_state(state, x)
if not state: break
else:
stack.append((input[:i+1], state, None))
if self.is_final(state):
# Input word is already valid
return input
# Perform a 'wall following' search for the
lexicographically smallest
# accepting state.
while stack:
path, state, x = stack.pop()
x = self.find_next_edge(state, x)
#print 'x'
if x:
path += x
state = self.next_state(state, x)
if self.is_final(state):
print 'p'
return path
stack.append((path, state, None))
print 'v'
return None
def find_next_edge(self, s, x):
if x is None:
x = '\0' # u'\0'
else:
x = chr(ord(x) + 1)
state_transitions = self.transitions.get(s, {})
if x in state_transitions or s in self.defaults:
return x
labels = sorted(state_transitions.keys())
pos = bisect.bisect_left(labels, x)
if pos < len(labels):
print 'n'
return labels[pos]
return None
def levenshtein_automata(self, term, k):# line 125 '
nfa = NFA((0, 0))
for i, c in enumerate(term):
for e in range(k + 1):
# Correct character
nfa.add_transition((i, e), c, (i + 1, e))
if e < k:
# Deletion
nfa.add_transition((i, e), NFA.ANY, (i, e + 1))
# Insertion
nfa.add_transition((i, e), NFA.EPSILON, (i + 1, e + 1))
Re: [Tutor] Python 2.7.1 interpreter complains about NameError: global name 'levenshtein_automata' is not defined
"Frank Chang" wrote
Good morning, I am using Python 2.7.1 on Windows XP Service Pack 3.
Here
is the program where the Python interpreter complains about
NameError:
global name 'levenshtein_automata' is not defined.
The others have answered the specific question, however I think you
have another problem lurking:
def find_all_matches(self, word, k, lookup_func):
lev = levenshtein_automata(word, k).to_dfa()
match = lev.next_valid_string('\0')
while match:
next = lookup_func(match)
if not next:
return
Here you return a None value
if match == next:
yield match
next1 = next1 + '\0'
match = lev.next_valid_string(next1)
length = len(list(testdfa.find_all_matches('food', 1, m)))
line 174
And here you try to convert the return value to a list.
But list(None) will fail with a TypeError.
You should probably returm an empty string or raise an exception
and catch it in your main block.
HTH,
--
Alan Gauld
Author of the Learn to Program web site
http://www.alan-g.me.uk/
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