Why does this list swap fail?
L=[2,1] L[0],L[L[0]-1]=L[L[0]-1],L[0] The L doesn't change. Can someone provide me the detail procedure of this expression? -- https://mail.python.org/mailman/listinfo/python-list
How make the judge with for loop?
c="abcdefghijk"
len=len(c)
n is a int
sb=[[] for i in range(n)]
while (i < len) {
for (int j = 0; j < n && i < len; j++)
sb[j].append(c[i++]);
for (int j = n-2; j >= 1 && i < len; j--) //
sb[j].append(c[i++]);
}
How to translate to python? I tried but my python code is really stupid
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Re: How to sort this without 'cmp=' in python 3?
在 2016年10月14日星期五 UTC-4下午7:35:08，38016...@gmail.com写道： > nums=['3','30','34','32','9','5'] > I need to sort the list in order to get the largest number string: '953433230' > > nums.sort(cmp=lambda a,b: cmp(a+b, b+a), reverse=True) > > But how to do this in python 3? > > Thank you !I learn more new tricks in Python. Thank you all of you guys. You are all very kind helpful and knowledgeable. -- https://mail.python.org/mailman/listinfo/python-list
How to sort this without 'cmp=' in python 3?
nums=['3','30','34','32','9','5'] I need to sort the list in order to get the largest number string: '953433230' nums.sort(cmp=lambda a,b: cmp(a+b, b+a), reverse=True) But how to do this in python 3? Thank you -- https://mail.python.org/mailman/listinfo/python-list
I am comfused about the name behavior of Python in recursion
Google told me Python name is a label attaching to the object. But in this recursive function,the name 'a' will point to different number object. def rec(a): a+=1 if a<10: rec(a) print(a) rec(0) gives me 101 normally.Why it works? Because of the stack memory management? Thank you -- https://mail.python.org/mailman/listinfo/python-list
Re: Need help for the print() function with a better order
在 2016年10月2日星期日 UTC-4下午1:05:58，Peter Pearson写道：
> On Sat, 1 Oct 2016 18:12:29 -0700 (PDT), 38016226...@gmail.com wrote:
> > I am trying to print a simple decision tree for my homework.
> > The answer must keep in this format:
> >
> > Top 7,4,0.95
> > career gain = 100
> > 1.Management 2, 3, 0.9709505944546686
> > 2.Service 5, 1, 0.6500224216483541
> > location gain = 100
> > 1.Oregon 4, 1, 0.7219280948873623
> > 2.California 3, 3, 1.0
> > edu_level gain = 100
> > 1.High School 5, 1, 0.6500224216483541
> > 2.College 2, 3, 0.9709505944546686
> > years_exp gain = 100
> > 1.Less than 3 3, 1, 0.8112781244591328
> > 2.3 to 10 2, 1, 0.9182958340544896
> > 3.More than 10 2, 2, 1.0
> >
> > Here is my code:
> > features={'edu_level':['High School',
> 'College'],
> 'career':['Management',
> 'Service'],
> 'years_exp':['Less than 3',
> '3 to 10',
> 'More than 10'],
> 'location':['Oregon',
> 'California']}
> >
> > print('Top 7,4,0.95')
> > for key in features:
> > print('{} gain = {}'.format(key,100))
> > attributes_list=features[key]
> > kargs={}
> > for i in range(len(attributes_list)):
> > kargs[key]=attributes_list[i]
> > low=table.count('Low',**kargs)
> > high=table.count('High',**kargs)
> > print('\t{}.{} {}, {}, {}'.format(
> i+1,attributes_list[i],low,high,entropy(low,high)))
> >
> > I set all the gain as 100 now.But actually the gain must calculate
> > with the data below. For example, the career gain need the data of
> > 'Management' and 'Service'. I don't know how to do. or Anyone can
> > provide me a better logic?
>
> I interpret your question as meaning that the value that you
> print after "gain =" should depend on features[key]. To do that,
> you'll need to insert a line resembling
> gain = gain_from_features(features[key])
> before the print statement. You'll have to write the gain_from_features
> function, and provide it with the numbers from which it will
> compute the gain.
>
> As a stylistic suggestion, note that Python allows you to break
> your "features=" line into a more readable format, as I have done
> above.
>
> Another stylistic suggestions:
> for key, attributes_list in features.iteritems():
>
> --
> To email me, substitute nowhere->runbox, invalid->com.
Thank you for your suggestion.I was so tired last night printing the structure
of decision tree crushed me.
I am not familiar with python and now I will try to modify my code.
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Need help for the print() function with a better order
I am trying to print a simple decision tree for my homework.
The answer must keep in this format:
Top 7,4,0.95
career gain = 100
1.Management 2, 3, 0.9709505944546686
2.Service 5, 1, 0.6500224216483541
location gain = 100
1.Oregon 4, 1, 0.7219280948873623
2.California 3, 3, 1.0
edu_level gain = 100
1.High School 5, 1, 0.6500224216483541
2.College 2, 3, 0.9709505944546686
years_exp gain = 100
1.Less than 3 3, 1, 0.8112781244591328
2.3 to 10 2, 1, 0.9182958340544896
3.More than 10 2, 2, 1.0
Here is my code:
features={'edu_level':['High School','College'],'career':
['Management','Service'],'years_exp':['Less than 3','3 to 10','More than
10'],'location':['Oregon','California']}
print('Top 7,4,0.95')
for key in features:
print('{} gain = {}'.format(key,100))
attributes_list=features[key]
kargs={}
for i in range(len(attributes_list)):
kargs[key]=attributes_list[i]
low=table.count('Low',**kargs)
high=table.count('High',**kargs)
print('\t{}.{} {}, {},
{}'.format(i+1,attributes_list[i],low,high,entropy(low,high)))
I set all the gain as 100 now.But actually the gain must calculate with the
data below.
For example, the career gain need the data of 'Management' and 'Service'.
I don't know how to do.
or Anyone can provide me a better logic?
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Is 'learning python 5th edition' a good book to beginner?
I want to find a python book like C++ primer which provides me details to understand the language. -- https://mail.python.org/mailman/listinfo/python-list
Why does the insert after list function fail?
A=["1","2","3"] print(list(map(float,A)).insert(0,1)) I want to insert 1 at the head of the list but this gives me a surprise -- https://mail.python.org/mailman/listinfo/python-list
Re: I am newbie who can explain this code to me?
在 2016年9月20日星期二 UTC-4下午3:11:27，Terry Reedy写道：
> On 9/20/2016 9:12 AM, Peter Otten wrote:
>
> >> 在 2016年9月20日星期二 UTC-4上午8:17:13，BartC写道：
> >>> On 20/09/2016 13:12, 38016226...@gmail.com wrote:
> >>> d = {}
> >>> keys = range(256)
> >>> vals = map(chr, keys)
> >>> map(operator.setitem, [d]*len(keys), keys, vals)
>
> It is from python library. What does [d]*len(keys) mean?
> d is the name of dict but put d in [] really confused me.
>
> Where in which 'python library? I cannot findI the above in 2.7 or 3.6
> stdlib. The code should be replaced by
>
> > It should be noted that the code above is really bad Python.
> > Better alternatives are the simple loop
> >
> > d = {}
> > for i in range(256):
> > d[i] = chr(i)
> >
> > or the dict comprehension
> >
> > d = {i: chr(i) for i in range(256)}
>
> this.
>
> --
> Terry Jan Reedy
I read an old 3.2 library and didn't notice at that time.
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Re: What does this zip() code mean?
在 2016年9月20日星期二 UTC-4上午9:35:50，Random832写道： > On Tue, Sep 20, 2016, at 09:19, 38016226...@gmail.com wrote: > > >>> x = [1, 2, 3] > > >>> y = [4, 5, 6] > > >>> zipped = zip(x, y) > > >>> list(zipped) > > [(1, 4), (2, 5), (3, 6)] > > >>> x2, y2 = zip(*zip(x, y)) > > >>> x == list(x2) and y == list(y2) > > True > > > > My problem is >>> x2, y2 = zip(*zip(x, y)). > > zip return an iterator but x2 and y2 are different? > > I really need detail explanation about this line. > > Well, as you've seen, zip(x, y) is (1, 4), (2, 5), (3, 6) > > This means that zip(*...) is zip((1, 4), (2, 5), (3, 6)). It takes the > first element of each argument (1, 2, and 3), and then the next element > of each argument (4, 5, and 6). thank you! -- https://mail.python.org/mailman/listinfo/python-list
Re: I am newbie who can explain this code to me?
在 2016年9月20日星期二 UTC-4上午9:13:35，Peter Otten写道：
> 38016226...@gmail.com wrote:
>
> > 在 2016年9月20日星期二 UTC-4上午8:17:13，BartC写道：
> >> On 20/09/2016 13:12, 38016226...@gmail.com wrote:
> >> d = {}
> >> keys = range(256)
> >> vals = map(chr, keys)
> >> map(operator.setitem, [d]*len(keys), keys, vals)
> >> >
> >> > It is from python library. What does [d]*len(keys) mean?
> >> > d is the name of dict but put d in [] really confused me.
> >> >
> >>
> >> if len(keys) is 5 then [d]*5 is:
> >>
> >> [d,d,d,d,d]
> >>
> >> [d] is a list, containing one item, a dict if that is what it is.
> >>
> >> --
> >> Bartc
> >
> > Thank you. I understand now
>
> It should be noted that the code above is really bad Python.
> Better alternatives are the simple loop
>
> d = {}
> for i in range(256):
> d[i] = chr(i)
>
> or the dict comprehension
>
> d = {i: chr(i) for i in range(256)}
>
> and even
>
> keys = range(256)
> d = dict(zip(keys, map(chr, keys)))
>
> because they don't build lists only to throw them away.
>
>
> Also, creating a list of dicts or lists is a common gotcha because after
>
> outer = [[]] * 3
>
> the outer list contains *the* *same* list three times, not three empty
> lists. Try
>
> outer[0].append("surprise")
> print(outer)
>
> in the interactive interpreter to see why the difference matters.
>
>
> Finally, if you are just starting you might consider picking Python 3
> instead of Python 2.
Thank you.I learn more!
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What does this zip() code mean?
>>> x = [1, 2, 3] >>> y = [4, 5, 6] >>> zipped = zip(x, y) >>> list(zipped) [(1, 4), (2, 5), (3, 6)] >>> x2, y2 = zip(*zip(x, y)) >>> x == list(x2) and y == list(y2) True My problem is >>> x2, y2 = zip(*zip(x, y)). zip return an iterator but x2 and y2 are different? I really need detail explanation about this line. -- https://mail.python.org/mailman/listinfo/python-list
Re: I am newbie who can explain this code to me?
在 2016年9月20日星期二 UTC-4上午8:17:13，BartC写道：
> On 20/09/2016 13:12, 38016226...@gmail.com wrote:
> d = {}
> keys = range(256)
> vals = map(chr, keys)
> map(operator.setitem, [d]*len(keys), keys, vals)
> >
> > It is from python library. What does [d]*len(keys) mean?
> > d is the name of dict but put d in [] really confused me.
> >
>
> if len(keys) is 5 then [d]*5 is:
>
> [d,d,d,d,d]
>
> [d] is a list, containing one item, a dict if that is what it is.
>
> --
> Bartc
Thank you. I understand now
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I am newbie who can explain this code to me?
>>> d = {}
>>> keys = range(256)
>>> vals = map(chr, keys)
>>> map(operator.setitem, [d]*len(keys), keys, vals)
It is from python library. What does [d]*len(keys) mean?
d is the name of dict but put d in [] really confused me.
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