[Tutor] How to use g_timeout_add () function?

[Lion Chen]

Hello all, i have a question:

when i check gtk_time_out in the gtk+2 reference, it said "
|gtk_timeout_add|has been deprecated since version 2.4 and should not be
used in newly-written code. Use |g_timeout_add()|instead."

but i don't know how tu use the g_timout_add() function:
my_id = g_timeout_add(500, myfunction())

or:

my_id = gtk.g_timeout_add(500, myfunction())

everytime i run the program, it prompted me a message like modules do
not have g_timeout_add() attribute.

so i still have to use gtk_timeout_add

anybody help me?

Lion Chen
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[Tutor] why gtk.Entry does not give me right answers?

[Lion Chen]

Hi, All,

i am trying write a calculator, now normal calculation works ok. but if
i enter long numbers, for example 33 + 7, it gives me
"12".

there are 18 "3"s, if the length is more than 17, the calculation will
be wrong on Windows and Ubuntu.

the following is some of my codes:

def pre_calc(self, op):
#if entry is empty, any operators are invalid except "-"
if not self.entry.get_text() and op != "-":
return

if not self.entry.get_text() and op == "-":
self.entry.set_text(op)
self.cleared = 1
self.negative_sign = True#indicates there's already a "-"
return

#retrieve the 1st num and operator
if not self.op and self.entry.get_text():
if op != "=":
self.op = op
#print "text typ:", type(self.entry.get_text())
self.first_num = self.entry.get_text()
self.cleared = 0 # ready to input 2nd num
#print "op:", self.op, "-", "1st num:", self.first_num
return
else:
self.first_num = None
self.second_num = None
self.op = None
self.cleared = 0
self.negative_sign = False
return

#retrieve the second num and begin calculation
elif self.op and self.first_num and self.entry.get_text() != "-":
if op == "=":
self.second_num = self.entry.get_text()
self.calc()
#reset the following varibles, awaiting next round of inputs
self.first_num = None
self.second_num = None
self.op = None
self.cleared = 0
self.negative_sign = False
return
elif op == "-":
if self.cleared == 1: #if user has input 2nd num already
self.second_num = self.entry.get_text()
self.calc()
self.first_num = self.entry.get_text()
self.op = op
self.cleared = 0
self.negative_sign = False
return
else:
self.entry.set_text(op)
self.cleared = 1
self.negative_sign = True#indicates there's already a "-"
return
else:
self.op = op
if self.cleared == 1:
self.second_num = self.entry.get_text()
self.calc()
self.first_num = self.entry.get_text()
self.cleared = 0
self.negative_sign = False
return
else:
return

def calc(self, unary_op = None):
if not unary_op:
if (not self.first_num) or (not self.second_num) or \
(not self.op):
return

result = None

calc_methods = {"+": self.add,
"-": self.subtract,
"*": self.multiply,
"/": self.divide,
"%": self.mod,
"pwr": self.power,
"|": self.b_or,
"&": self.b_and,
"^": self.b_exc,
"<<": self.b_lshift,
">>": self.b_rshift
}

unary_methods ={"~": self.b_invert,
"1/x": self.a_fraction,
"sqrt": self.sqrt
}

if not unary_op:
for op, method in calc_methods.items():
if self.op == op:
result = calc_methods[op]()
else:
for op, method in unary_methods.items():
if unary_op == op:
result = unary_methods[op]()

self.entry.set_text(result)

def add(self):
result = None
#if hex system
#print type(self.first_num)
if self.hdob["h"].get_active():
self.first_num = long(self.first_num, 16)
self.second_num = long(self.second_num, 16)
r = self.first_num + self.second_num

r = self.convert.d2h(r)

return r

#if decimal system
elif self.hdob["d"].get_active():
self.first_num = float(self.first_num)
self.second_num = float(self.second_num)
result = self.first_num + self.second_num

if result - long(result) == 0:
#print str(long(result))
return str(long(result))
else:
return str(result)

#if octal system
elif self.hdob["o"].get_active():
self.first_num = long(self.first_num, 8)
self.second_num = long(self.second_num, 8)
result = self.first_num + self.second_num

result = self.convert.d2o(result)

return result

else:
self.first_num = long(self.first_num, 2)
self.second_num = long(self.second_num, 2)
result = bin(self.first_num + self.second_num)

result = self.convert.d2b(result)

return result

but if i run the following codes on command line, it works ok:

>>>a = 33L
>>>b= str(a)
>>>b
'33'

why? i don't understand

anybody can help me?  thanks.

Lion

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Re: [Tutor] why gtk.Entry does not give me right answers?

[Lion Chen]

于 2012年04月23日 23:08, Steven D'Aprano 写道:

Lion Chen wrote:

Hi, All,

i am trying write a calculator, now normal calculation works ok. but if
i enter long numbers, for example 33 + 7, it gives me
"12".

there are 18 "3"s, if the length is more than 17, the calculation will
be wrong on Windows and Ubuntu.

You are losing precision by converting into a float. Watch:


n = 33
n + 7

40

int(float(n))

12

int(float(n)+7)

12

Your integer value 333...333 requires 59 bits to store the entire number, but
Python floats are C doubles, which only have 52 bits available for the numeric
digits. (The other 12 bits encode the sign and exponent.)

http://www.johndcook.com/blog/2009/04/06/anatomy-of-a-floating-point-number/

You cannot store ...333 exactly as a float. The two closest floats are:

12.0
76.0

so all numbers between them will be rounded up or down.

Some possible solutions:

* Don't try to mix infinite-precision integer arithmetic with finite-precision
   float arithmetic.

* Don't convert to float unless you really need to, e.g. if the string
   contains a decimal point.

* Use the decimal module instead of floats. You still have finite precision,
   but you can choose how many *decimal* places to store instead of having a
   fixed number of *binary* places. (But decimal is much slower.)


By the way, the code that you sent is unreadable. Please make sure that you
send plain text email, and that indentation is not lost. Without indentation,
it is impossible to understand your code.


many thanks, Steve, i see, and i have solved it :) .

and the codes in my thunderbird shows ok, so i thought it would be ok in 
yours, sorry for that


Lion





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[Tutor] gtk.TreeView displays all right on Windows, but can't see the values on Ubuntu

[Lion Chen]

Hi, All,
first thanks the people who gave helps to me, :)

now i encountered another question...
my first program LionCalculator, works ok on Windows, but there is a
problem on Ubuntu.

LionCalculator has a function that can store the previous calculation
results to the
gtk.ListStore((gobject.TYPE_STRING, gobject.TYPE_BOOLEAN,
gobject.TYPE_STRING))

for i in xrange(12):
self.results_store.append(["F%d" % (i+1), None, None])

when pressed F1--F12 or click the gtk.CellRendererRadio, the gtk.Entry
will get the corresbonding values stored in ListStore.

when i run the program on Windows, no problem, i can see everything that
should display on the screen. but when i run it on Ubuntu, i can't see
the "F1" -- "F12" in the ListStore, can't see the calculation results
that should also display on ListStore, only the gtk.CellRendererRadio
showed.
i don't understand...

and when i add "print ...get_store()[0][0]" and run it again, it print
"F1"! strange... and when i press F1 or F2..., the result will copy to
the entry,
although it does not display in the TreeView, strange...

the following are codes:

#in class ResultsView..
def make_view(self):
# make ListStore for storing results
self.results_store = gtk.ListStore(gobject.TYPE_STRING,
gobject.TYPE_BOOLEAN,
gobject.TYPE_STRING)

#to store 12 calculation results, the results_store[0][0] is "F1--F12"
for i in xrange(12):
self.results_store.append(["F%d" % (i+1), None, None])

self.results_view = gtk.TreeView(self.results_store)

#f_renderer is for "F1" -- "F12"
f_renderer = gtk.CellRendererText()
f_renderer.set_property( 'editable', False )
f_renderer.set_property("size", 5)
f_renderer.set_property("cell-background", "cyan")

#when clicked bt_renderer, it will copy the corresbonding values to
gtk.entry
bt_renderer = gtk.CellRendererToggle()
bt_renderer.set_property('activatable', True)
bt_renderer.set_property("radio", True)
bt_renderer.set_property("cell-background", "grey")
bt_renderer.connect("toggled", self.ready_cp, self.results_store)

#txt_renderer is for storing calculation results
txt_renderer = gtk.CellRendererText()
txt_renderer.set_property( 'editable', False )
txt_renderer.set_property("size", 5)
txt_renderer.set_property("cell-background", "green")

#i guess the problem is in the following, but i don't know where it
exactly is, ok in Windows, can't show in Ubuntu...
bt_column = gtk.TreeViewColumn("F1--F12")
bt_column.pack_start(f_renderer, True)
bt_column.pack_start(bt_renderer, False)
bt_column.set_attributes(f_renderer, text=0)
#set active to be clickable. and the bt_columen is
#corresbonding to results_store columne 1
bt_column.add_attribute(bt_renderer, "active", 1)

#and txt_column is corresbonding to the store column 2
txt_column = gtk.TreeViewColumn("Calculation Results ", txt_renderer,
text=2)
self.results_view.append_column(bt_column)
self.results_view.append_column(txt_column)

self.results_view.show()

return self.results_view

#in class LionCalc
def __init__(self):
..
self.results_view = ResultsView()
right_vbox.pack_start(self.results_view.make_view(), True, True, 0)

win.show_all()

could anybody give me help? thanks.

-- 
Lion Chen

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[Tutor] why list is not thread-safe, but deque and queue are thread-safe?

[Lion Chen]

Hi, All,
i can not understand why list is not thread-safe, but deque and queue
are thread-safe?

that's all. thanks.

Lion Chen
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Re: [Tutor] why list is not thread-safe, but deque and queue are thread-safe?

[Lion Chen]

i have read it, as the "Answer" said, seems like deque is not 
thread-safe either, because deque has the operator +=, and others like that.


i got some material about atomoperation from google:

An operation during which a processor 
<http://www.webopedia.com/TERM/M/microprocessor.html> can simultaneously 
read <http://www.webopedia.com/TERM/R/read.html> a location and write 
<http://www.webopedia.com/TERM/W/write.html> it in the same bus 
<http://www.webopedia.com/TERM/B/bus.html> operation. This prevents any 
other processor or I/O <http://www.webopedia.com/TERM/I/I_O.html> device 
<http://www.webopedia.com/TERM/D/device.html> from writing or reading 
memory until the operation is complete./
Atomic/ implies indivisibility and irreducibility, so an atomic 
operation must be performed entirely or not performed at all.


so deque is not thread-safe either. right?

http://stackoverflow.com/questions/6319207/are-lists-thread-safe



On Wed, May 2, 2012 at 7:58 PM, Lion Chen <mailto:chnlio...@gmail.com>> wrote:


Hi, All,
i can not understand why list is not thread-safe, but deque and queue
    are thread-safe?

that's all. thanks.

Lion Chen
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--
http://spawgi.wordpress.com
We can do it and do it better.


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[Tutor] why i < j is True, j < k is False

[Lion Chen]

Hi, All,
here are the codes:

class a:
pass


i = a ()
j = a ()
k = a ()

i < j returns True

j < k returns False

why?

Lion Chen
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Re: [Tutor] why i < j is True, j < k is False

[Lion Chen]

On Fri, May 4, 2012 at 9:29 AM, Lion Chen  wrote:

Hi, All,
here are the codes:

class a:
pass


i = a ()
j = a ()
k = a ()

i<  j returns True

j<  k returns False

why?

Lion Chen
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Did you look at what I, j, and k are?  They are names of objects.
When I ran your code my inequalities were different.
What you are seeing is likely some comparison of the location of the
objects over which you have no control

i = a()
j = a()
k = a()
i<  j

False

j<  k

True

i

<__main__.a instance at 0xb76d0a2c>

j

<__main__.a instance at 0xb76d096c>

k

<__main__.a instance at 0xb76d09ec>
but why have i got the same results every time i run the codes?
even when i restart the python interpreter,  seems like i, j, k have the 
fixed values.





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Re: [Tutor] why i < j is True, j < k is False

[Lion Chen]

于 2012年05月04日 22:12, Dave Angel 写道:

On 05/04/2012 09:29 AM, Lion Chen wrote:

Hi, All,
here are the codes:

class a:
pass


i = a ()
j = a ()
k = a ()

i<  j returns True

j<  k returns False

why?

Lion Chen
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i, j and k are three distinct instances of the class a  (which should be
capitalized for clarity).

Since you don't supply any comparison operator special methods in your
class, Python 2 simply compares their id values.  So the ordering is
entirely undefined, and each of us might get different results. I, for
example, got true and true.

In Python 3, you'd get the following error, which is an improvement, imho:

TypeError: unorderable types: A()<  A()


i see, thanks  :)

Lion Chen




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