array of array of float

[Summercoolness]

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]

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]

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/showfiles.php?group_id=1369&package_id=175103
main page:
http://numeric.scipy.org/

 

[=?ISO-8859-1?Q?Sch=FCle_Daniel?=]

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)]

 

[=?ISO-8859-1?Q?Sch=FCle_Daniel?=]

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]

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]

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

correction

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

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

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