array of array of float

[Summercoolness@gmail.com]

i used C too much and haven't used Python for a while...

like in C, if we want an array of array of float, we use

float a[200][500];

now in Python, seems like we have to do something like

a = [ [ ] ] * 200

and then just use

a[1].append(12.34) etc

but it turns out that all 200 elements points to the same list...
and i have to use

a = [ ]
for i in range (0, 200):
a.append([ ])

is there a simpler way... i wonder...

[Fredrik Lundh]

Re: array of array of float

Summercoolness@ gmail.com wrote:

i used C too much and haven't used Python for a while...
>
like in C, if we want an array of array of float, we use
>
float a[200][500];
>
now in Python, seems like we have to do something like
>
a = [ [ ] ] * 200
>
and then just use
>
a[1].append(12.34) etc
>
but it turns out that all 200 elements points to the same list...
and i have to use
>
a = [ ]
for i in range (0, 200):
a.append([ ])
>
is there a simpler way... i wonder...

this is FAQ:

http://pyfaq.infogami.com/how-do-i-create-a-multidimensional-list

</F>

[DH]

Re: array of array of float

Summercoolness@ gmail.com wrote:

i used C too much and haven't used Python for a while...
>
like in C, if we want an array of array of float, we use
>
float a[200][500];
>
now in Python, seems like we have to do something like
>
a = [ [ ] ] * 200
>
and then just use
>
a[1].append(12.34) etc
>
but it turns out that all 200 elements points to the same list...
and i have to use
>
a = [ ]
for i in range (0, 200):
a.append([ ])
>
is there a simpler way... i wonder...
>

Right, try the numpy module, and you can do:

from numpy import *
a = zeros((200,500) , Float)

documentation:

http://numeric.scipy.org/numpydoc/numpy-6.html#pgfId-60291

download:
http://sourceforge.net/project/showf...kage_id=175103
main page:

http://numeric.scipy.org/

[Schüle Daniel]

Re: array of array of float

Summercoolness@ gmail.com schrieb:

i used C too much and haven't used Python for a while...
>
like in C, if we want an array of array of float, we use
>
float a[200][500];
>
now in Python, seems like we have to do something like
>
a = [ [ ] ] * 200
>
and then just use
>
a[1].append(12.34) etc
>
but it turns out that all 200 elements points to the same list...
and i have to use
>
a = [ ]
for i in range (0, 200):
a.append([ ])
>
is there a simpler way... i wonder...

a = [[] for in range(200)]

[Schüle Daniel]

Re: array of array of float

Schüle Daniel schrieb:

Summercoolness@ gmail.com schrieb:

>i used C too much and haven't used Python for a while...
>>
>like in C, if we want an array of array of float, we use
>>
>float a[200][500];
>>
>now in Python, seems like we have to do something like
>>
>a = [ [ ] ] * 200
>>
>and then just use
>>
>a[1].append(12.34) etc
>>
>but it turns out that all 200 elements points to the same list...
>and i have to use
>>
>a = [ ]
>for i in range (0, 200):
> a.append([ ])
>>
>is there a simpler way... i wonder...

>
a = [[] for in range(200)]

correction :)

a = [[] for i in range(200)]

[tac-tics]

Re: array of array of float

Use nested list comprehensions:

matrix = [[0.0 for x in xrange(n)] for y in xrange(m)]

This is similar to "float matrix[m][n]" in C.

All cells are independent of each other in doing this.

[Fredrik Lundh]

Re: array of array of float

"Schüle Daniel" wrote:

a = [[] for in range(200)]

>
correction :)
>
a = [[] for i in range(200)]

the "*500" part still seems to be missing...

</F>