[Tutor] How many times X is in a list?
Hello,
Can you help me with this please?
I have a list that contains elements to be created (in a 3D app), in the
list each element is a dictionary that contains data, like:
Elements = [
{'Width': 3.0, 'Depth': 3.0, 'Name': 'Access', 'Parent':
'Plot', 'Height': 3.0},
{'Width': 3.0, 'Depth': 3.0, 'Name': 'Circulation_01',
'Parent': 'Access', 'Height': 3.0},
{'Width': 3.0, 'Depth': 3.0, 'Name': 'Circulation_02',
'Parent': 'Access', 'Height': 3.0},
{'Width': 3.0, 'Depth': 3.0, 'Name': 'Circulation_03',
'Parent': 'Access', 'Height': 3.0},
{'Width': 2.0, 'Depth': 6.0, 'Name': 'Int_Circ_01',
'Parent': 'Circulation_01', 'Height': 3.0},
{'Width': 2.0, 'Depth': 5.0, 'Name': 'Int_Circ_02',
'Parent': 'Circulation_01', 'Height': 3.0},
{'Width': 2.0, 'Depth': 6.5, 'Name': 'Int_Circ_03',
'Parent': 'Circulation_02', 'Height': 3.0},
{'Width': 2.0, 'Depth': 5.0, 'Name': 'Int_Circ_04',
'Parent': 'Circulation_02', 'Height': 3.0},
{'Width': 2.0, 'Depth': 5.0, 'Name': 'Int_Circ_05',
'Parent': 'Circulation_03', 'Height': 3.0},
{'Width': 2.0, 'Depth': 5.0, 'Name': 'Int_Circ_06',
'Parent': 'Circulation_03', 'Height': 3.0},
]
so a for loop is used to iterate the list, like:
for element in elements:
create object with the desired width, depth, name, etc
The thing is that there can only be a "Circulation" by story, so I am
thinking in adding each created object to a built_Objects list and
appending the created object to the list, like:
for element in elements:
create element
append element['Name'] to built_Objects
My question is, how can I check how many times "Circulation" appears in
the built_Objects list? I think that if I get the number of times /N/
that "Circulation" appears I can multiply the next circulation elevation
/N/ times and avoid having two circulations in the same level. Is this a
correct reasoning?
I did a little research and found that count could help me, so I tried:
print Built_Elements.count('Circulation')
but well is not working. The result is 0, I guess that count is looking
for the exact term and not something similar
If you know the solution or a better way to do this please let me know.
Thanks in advance,
Carlos
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Re: [Tutor] How many times X is in a list?
Carlos wrote:
> Hello,
>
> Can you help me with this please?
>
> I have a list that contains elements to be created (in a 3D app), in the
> list each element is a dictionary that contains data, like:
>
> Elements = [
> {'Width': 3.0, 'Depth': 3.0, 'Name': 'Access', 'Parent':
> 'Plot', 'Height': 3.0},
> {'Width': 3.0, 'Depth': 3.0, 'Name': 'Circulation_01',
> 'Parent': 'Access', 'Height': 3.0},
> {'Width': 3.0, 'Depth': 3.0, 'Name': 'Circulation_02',
> 'Parent': 'Access', 'Height': 3.0},
> {'Width': 3.0, 'Depth': 3.0, 'Name': 'Circulation_03',
> 'Parent': 'Access', 'Height': 3.0},
> {'Width': 2.0, 'Depth': 6.0, 'Name': 'Int_Circ_01',
> 'Parent': 'Circulation_01', 'Height': 3.0},
> {'Width': 2.0, 'Depth': 5.0, 'Name': 'Int_Circ_02',
> 'Parent': 'Circulation_01', 'Height': 3.0},
> {'Width': 2.0, 'Depth': 6.5, 'Name': 'Int_Circ_03',
> 'Parent': 'Circulation_02', 'Height': 3.0},
> {'Width': 2.0, 'Depth': 5.0, 'Name': 'Int_Circ_04',
> 'Parent': 'Circulation_02', 'Height': 3.0},
> {'Width': 2.0, 'Depth': 5.0, 'Name': 'Int_Circ_05',
> 'Parent': 'Circulation_03', 'Height': 3.0},
> {'Width': 2.0, 'Depth': 5.0, 'Name': 'Int_Circ_06',
> 'Parent': 'Circulation_03', 'Height': 3.0},
> ]
>
> so a for loop is used to iterate the list, like:
>
> for element in elements:
> create object with the desired width, depth, name, etc
>
> The thing is that there can only be a "Circulation" by story, so I am
> thinking in adding each created object to a built_Objects list and
> appending the created object to the list, like:
>
> for element in elements:
> create element
> append element['Name'] to built_Objects
>
> My question is, how can I check how many times "Circulation" appears in
> the built_Objects list? I think that if I get the number of times /N/
> that "Circulation" appears I can multiply the next circulation elevation
> /N/ times and avoid having two circulations in the same level. Is this a
> correct reasoning?
>
> I did a little research and found that count could help me, so I tried:
>
> print Built_Elements.count('Circulation')
>
> but well is not working. The result is 0, I guess that count is looking
> for the exact term and not something similar
>
> If you know the solution or a better way to do this please let me know.
Yes, count() is looking for exact matches. You can make a new list with
just the circulation names and take the length of that; something like this:
len([name for name in built_Objects if name.startswith('Circulation')])
or perhaps slightly more efficient (Python 2.5):
sum(1 for name in built_Objects if name.startswith('Circulation'))
Kent
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Re: [Tutor] How many times X is in a list?
> Yes, count() is looking for exact matches. You can make a new list with
> just the circulation names and take the length of that; something like this:
> len([name for name in built_Objects if name.startswith('Circulation')])
>
> or perhaps slightly more efficient (Python 2.5):
> sum(1 for name in built_Objects if name.startswith('Circulation'))
>
I thought sum only worked on lists.
Is that supposed to be a list comprehension inside of sum or am I wrong?
(still using 2.4.3, so I can't check)
Thanks,
-Luke
> Kent
>
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>
>
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Re: [Tutor] How many times X is in a list?
Luke Paireepinart wrote:
>> Yes, count() is looking for exact matches. You can make a new list with
>> just the circulation names and take the length of that; something like this:
>> len([name for name in built_Objects if name.startswith('Circulation')])
>>
>> or perhaps slightly more efficient (Python 2.5):
>> sum(1 for name in built_Objects if name.startswith('Circulation'))
>>
> I thought sum only worked on lists.
According to the docs sum() works on sequences, but in fact it seems to
work on any iterable (a weaker condition than sequence). For example you
can sum a dict which is not a sequence:
In [4]: d=dict.fromkeys(range(10))
In [6]: sum(d)
Out[6]: 45
> Is that supposed to be a list comprehension inside of sum or am I wrong?
No, it is a generator comprehension which is like a list comp except it
uses () instead of [] and it creates an iterator rather than a list.
The reason I postulate that using sum() *might* be more efficient is
because it doesn't have to create the intermediate list. Of course for
any reasonable size list it won't make a noticable difference anyway...
Kent
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Re: [Tutor] How many times X is in a list?
Thanks Kent,
That solves it pretty well.
Carlos
Kent Johnson wrote:
> Yes, count() is looking for exact matches. You can make a new list
> with just the circulation names and take the length of that; something
> like this:
> len([name for name in built_Objects if name.startswith('Circulation')])
>
> or perhaps slightly more efficient (Python 2.5):
> sum(1 for name in built_Objects if name.startswith('Circulation'))
>
> Kent
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