howto make Python list from numpy.array?

[dmitrey]

howto make Python list from numpy.array?
Thx, D.

[John Nagle]

Re: howto make Python list from numpy.array?

dmitrey wrote:

howto make Python list from numpy.array?
Thx, D.
>

lst = map(None, arr) // for 1D arrays.

John Nagle

[Terry Reedy]

Re: howto make Python list from numpy.array?


"dmitrey" <openopt@ukr.ne twrote in message
news:1178480447 .245977.293010@ n59g2000hsh.goo glegroups.com.. .
| howto make Python list from numpy.array?

I Googled 'numpy array Python list' and looked at the third hit
(PythonBasics) and at the bottom found your answer. About 30 seconds or
less.

tjr

[Amaury Forgeot d'Arc]

Re: howto make Python list from numpy.array?

Hello,

John Nagle a écrit :

dmitrey wrote:

>howto make Python list from numpy.array?
>Thx, D.
>>

>
lst = map(None, arr) // for 1D arrays.

Which can be expressed more simply as:
lst = list(arr)


--
Amaury

[dmitrey]

Re: howto make Python list from numpy.array?

Thanks all.
I tried all the approaches but they don't work in my situation
I have a variable x that can be
x = 1
x = [1, 2, 3]
x = numpy.array([1,2,3])
so all troubles are with 1st case

>>x=1
>>list(x)

Traceback (most recent call last):
File "<string>", line 1, in <string>
TypeError: iteration over non-sequence

>>list(array(1) )

Traceback (most recent call last):
File "<string>", line 1, in <string>
ValueError: Rank-0 array has no length.

>>array(1).toli st()

Traceback (most recent call last):
File "<string>", line 1, in <string>
ValueError: rank-0 arrays don't convert to lists.

>>>

Here I used Python 2.4.3, numpy 1.02

[Robert Kern]

Re: howto make Python list from numpy.array?

Amaury Forgeot d'Arc wrote:

Hello,
>
John Nagle a écrit :

>dmitrey wrote:

>>howto make Python list from numpy.array?
>>Thx, D.
>>>

>lst = map(None, arr) // for 1D arrays.

>
Which can be expressed more simply as:
lst = list(arr)

For N-D arrays, that will give you a list of arrays. If you want a list of lists
(of lists of lists ... etc N times), use the .tolist() method of arrays.

--
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
that is made terrible by our own mad attempt to interpret it as though it had
an underlying truth."
-- Umberto Eco

[Robert Kern]

Re: howto make Python list from numpy.array?

dmitrey wrote:

Thanks all.
I tried all the approaches but they don't work in my situation
I have a variable x that can be
x = 1
x = [1, 2, 3]
x = numpy.array([1,2,3])
so all troubles are with 1st case

>>>x=1
>>>list(x)

Traceback (most recent call last):
File "<string>", line 1, in <string>
TypeError: iteration over non-sequence

>>>list(array(1 ))

Traceback (most recent call last):
File "<string>", line 1, in <string>
ValueError: Rank-0 array has no length.

>>>array(1).tol ist()

Traceback (most recent call last):
File "<string>", line 1, in <string>
ValueError: rank-0 arrays don't convert to lists.
>
Here I used Python 2.4.3, numpy 1.02

All of these results are entirely correct. A scalar (or rank-0 array) is not a
sequence.

If you have a need to transform a scalar into a sequence (e.g. transform 1 to
[1]), then you can use numpy.atleast_1 d(x).tolist().

--
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
that is made terrible by our own mad attempt to interpret it as though it had
an underlying truth."
-- Umberto Eco

[Steven D'Aprano]

Re: howto make Python list from numpy.array?

On Sun, 06 May 2007 13:06:56 -0700, dmitrey wrote:

Thanks all.
I tried all the approaches but they don't work in my situation
I have a variable x that can be
x = 1
x = [1, 2, 3]
x = numpy.array([1,2,3])
so all troubles are with 1st case

And yet your question was about the third case:

"howto make Python list from numpy.array?"


You should have asked:

How do I make a Python list from an int?

And the answer would be:

x = 1
lst = [x]

Another answer would be:

x = 1
lst = ["existing", "list"]
lst.append(x)



--
Steven.