Develop Reference

How to copy a specific range between two mmap?

How is it possible to only copy a specific part of one mmap into another via slices?
#!/usr/bin/python3
import mmap
a = mmap.mmap(-1, 5)
b = mmap.mmap(-1, 5)
a[0:] = b'12345'
b[0:] = b'67890'
a[2:6] = b[0:4]
print(a[:])
Is there a way to copy such a range via slices? If this is not possible, what other solutions exist?

I think you mush be getting below error:
IndexError: mmap slice assignment is wrong size
change a[2:6] = b[0:4] to
a[1:5] = b[0:4]
output:
b'16789' # print(a[:])

Although it isn't really clear what you are expecting, the above code will not work because you are using an invalid range. Calling a[2:6] will return a slice of size three, (i.e. it will return a[2:5] since a[6] doesn't actually exist) resulting in an error IndexError: mmap slice assignment is wrong size
Try running this with a[1:5] = b[0:4]. This yields:
print(a[:])
b'16789'

change shader on all assigned meshes, without using hyperShade()

I get all shapes assigned to baseMaterial, select the shapes and then assign the occlusionShader.
for materialClass in materialClassList:
select(materialClass.baseMaterial)
hyperShade(objects="")
hyperShade(a=materialClass.occlusionShader)
works just fine, but if I use it as a pre render script:
Error: line 0: hyperShade command not supported in batch mode
What can I change the two last lines of my function to to make this work?

Here is an example with cmds.sets() to assign a shader :
all = cmds.ls(type='mesh')
shadingEngine = 'initialShadingGroup'
cmds.sets(all, e=True, forceElement=shadingEngine)
as you can guess, to query meshes with the material :
lamb1_mshs = cmds.sets(shadingEngine, q=True)

i got it to work with:
for materialClass in materialClassList:
sets(materialClass.occlusionShadingGroup, e = True, forceElement = materialClass.meshList)
I collect the meshes when I create the materialClass now, which makes much more sense then selecting them for each renderlayer.

Save all values of a variable (in a loop) in another variable in Python

I have a code that I inform a folder, where it has n images that the code should return me the relative frequency histogram.
From there I have a function call:
for image in total_images:
histogram(image)
Where image is the current image that the code is working on and total_images is the total of images (n) it has in the previously informed folder.
And from there I call the histogram() function, sending as a parameter the current image that the code is working.
My histogram() function has the purpose of returning the histogram of the relative frequency of each image (rel_freq).
Although the returned values ​​are correct, rel_freq should be a array 1x256 positions ranging from 0 to 255.
How can I transform the rel_freq variable into a 1x256 array? And each value stored in its corresponding position?
When I do len *rel_freq) it returns me 256, that's when I realized that it is not in the format I need...
Again, although the returned data is correct...
After that, I need to create an array store_all = len(total_images)x256 to save all rel_freq...
I need to save all rel_freq in an array to later save it and to an external file, such as .txt.
I'm thinking of creating another function to do this...
Something like that, but I do not know how to do it correctly, but I believe you will understand the logic...
def store_all_histograms(total_images):
n = len(total_images)
store_all = [n][256]
for i in range(0,n):
store_all[i] = rel_freq
I know the function store_all_histograms() is wrong, I just wrote it here to show more or less the way I'm thinking of doing... but again, I do not know how to do it properly... At this point, the error I get is:
store_all = [n][256]
IndexError: list index out of range
After all, I need the store_all variable to save all relative frequency histograms for example like this:
position: 0 ... 256
store_all = [
[..., ..., ...],
[..., ..., ...],
.
.
.
n
]
Now follow this block of code:
def histogram(path):
global rel_freq
#Part of the code that is not relevant to the question...
rel_freq = [(float(item) / total_size) * 100 if item else 0 for item in abs_freq]
def store_all_histograms(total_images):
n = len(total_images)
store_all = [n][256]
for i in range(0,n):
store_all[i] = rel_freq
#Part of the code that is not relevant to the question...
# Call the functions
for fn in total_images:
histogram(fn)
store_all_histograms(total_images)
I hope I have managed to be clear with the question.
Thanks in advance, if you need any additional information, you can ask me...

Return the result, don't use a global variable:
def histogram(path):
return [(float(item) / total_size) * 100 if item else 0 for item in abs_freq]
Create an empty list:
store_all = []
and append your results:
for fn in total_images:
store_all.append(histogram(fn))
Alternatively, use a list comprehension:
store_all = [histogram(fn) for fn in total_images]

for i in range(0,n):
store_all[i+1] = rel_freq
Try this perhaps? I'm a bit confused on the question though if I'm honest. Are you trying to shift the way you call the array with all the items by 1 so that instead of calling position 1 by list[0] you call it via list[1]?
So you want it to act like this?
>>list = [0,1,2,3,4]
>>list[1]
0

How to use function like matlab 'fread' in python?

This is a .dat file.
In Matlab, I can use this code to read.
lonlatfile='NOM_ITG_2288_2288(0E0N)_LE.dat';
f=fopen(lonlatfile,'r');
lat_fy=fread(f,[2288*2288,1],'float32');
lon_fy=fread(f,[2288*2288,1],'float32')+86.5;
lon=reshape(lon_fy,2288,2288);
lat=reshape(lat_fy,2288,2288);
Here are some results of Matlab:
matalab
How to do in python to get the same result?
PS: My code is this:
def fromfileskip(fid,shape,counts,skip,dtype):
"""
fid : file object, Should be open binary file.
shape : tuple of ints, This is the desired shape of each data block.
For a 2d array with xdim,ydim = 3000,2000 and xdim = fastest
dimension, then shape = (2000,3000).
counts : int, Number of times to read a data block.
skip : int, Number of bytes to skip between reads.
dtype : np.dtype object, Type of each binary element.
"""
data = np.zeros((counts,) + shape)
for c in range(counts):
block = np.fromfile(fid,dtype=np.float32,count=np.product(shape))
data[c] = block.reshape(shape)
fid.seek( fid.tell() + skip)
return data
fid = open(r'NOM_ITG_2288_2288(0E0N)_LE.dat','rb')
data = fromfileskip(fid,(2288,2288),1,0,np.float32)
loncenter = 86.5 #Footpoint of FY2E
latcenter = 0
lon2e = data+loncenter
lat2e = data+latcenter
Lon = lon2e.reshape(2288,2288)
Lat = lat2e.reshape(2288,2288)
But, the result is different from that of Matlab.

You should be able to translate the code directly into Python with little change:
lonlatfile = 'NOM_ITG_2288_2288(0E0N)_LE.dat'
with open(lonlatfile, 'rb') as f:
lat_fy = np.fromfile(f, count=2288*2288, dtype='float32')
lon_fy = np.fromfile(f, count=2288*2288, dtype='float32')+86.5
lon = lon_ft.reshape([2288, 2288], order='F');
lat = lat_ft.reshape([2288, 2288], order='F');
Normally the numpy reshape would be transposed compared to the MATLAB result, due to different index orders. The order='F' part makes sure the final output has the same layout as the MATLAB version. It is optional, if you remember the different index order you can leave that off.
The with open() as f: opens the file in a safe manner, making sure it is closed again when you are done even if the program has an error or is cancelled for whatever reason. Strictly speaking it is not needed, but you really should always use it when opening a file.

How to index an array value in a MATLAB-Function in Simulink?

I'm using a matlab-function in simulink to call a python script, that do some calculations from the input values. The python-script gives me a string back to the matlab-function, that I split to an array. The splitted string has always to be a cell array with 6 variable strings:
dataStringArray = '[[-5.01 0.09785429][-8.01 0.01284927]...' '10.0' '20.0' '80.0' '80.0' '50.0'
To call the functions like strsplit or the python-script itself with a specific m-file, I'm using coder.extrinsic('*') method.
Now I want to index to a specific value for example with dataStringArray(3) to get '20.0' and define it as an output value of the matlab-function, but this doesn't work! I tried to predefine the dataStringArray with dataStringArray = cell(1,6); but get always the same 4 errors:
Subscripting into an mxArray is not supported.
Function 'MATLAB Function' (#23.1671.1689), line 42, column 24:
"dataStringArray(3)"
2x Errors occurred during parsing of MATLAB function 'MATLAB Function'
Error in port widths or dimensions. Output port 1 of 's_function_Matlab/MATLAB Function/constIn5' is a one dimensional vector with 1 elements.
What do I'm wrong?
SAMPLE CODE
The commented code behind the output definitions is what I need.:
function [dataArrayOutput, constOut1, constOut2, constOut3, constOut4, constOut5] = fcn(dataArrayInput, constIn1, constIn2, constIn3, constIn4, constIn5)
coder.extrinsic('strsplit');
% Python-Script String Output
pythonScriptOutputString = '[[-5.01 0.088068861]; [-4.96 0.0]]|10.0|20.0|80.0|80.0|50.0';
dataStringArray = strsplit(pythonScriptOutputString, '|');
% Outputs
dataArrayOutput = dataArrayInput; % str2num(char((dataStringArray(1))));
constOut1 = constIn1; % str2double(dataStringArray(2));
constOut2 = constIn2; % str2double(dataStringArray(3));
constOut3 = constIn3; % str2double(dataStringArray(4));
constOut4 = constIn4; % str2double(dataStringArray(5));
constOut5 = constIn5; % str2double(dataStringArray(6));
SOLUTION 1
Cell arrays are not supported in Matlab function blocks, only the native Simulink datatypes are possible.
A workaround is to define the whole code as normal function and execute it from the MATLAB-Function defined with extrinsic. It`s important to initialize the output variables with a known type and size before executing the extrinsic function.
SOLUTION 2
Another solution is to use the strfind function, that gives you a double matrix with the position of the splitter char. With that, you can give just the range of the char positions back that you need. In this case, your whole code will be in the MATLAB-Function block.
function [dataArrayOutput, constOut1, constOut2, constOut3, constOut4, constOut5] = fcn(dataArrayInput, constIn1, constIn2, constIn3, constIn4, constIn5)
coder.extrinsic('strsplit', 'str2num');
% Python-Script String Output
pythonScriptOutputString = '[[-5.01 0.088068861]; [-4.96 0.0]; [-1.01 7.088068861]]|10.0|20.0|80.0|80.0|50.0';
dataStringArray = strfind(pythonScriptOutputString,'|');
% preallocate
dataArrayOutput = zeros(3, 2);
constOut1 = 0;
constOut2 = 0;
constOut3 = 0;
constOut4 = 0;
constOut5 = 0;
% Outputs
dataArrayOutput = str2num(pythonScriptOutputString(1:dataStringArray(1)-1));
constOut1 = str2num(pythonScriptOutputString(dataStringArray(1)+1:dataStringArray(2)-1));
constOut2 = str2num(pythonScriptOutputString(dataStringArray(2)+1:dataStringArray(3)-1));
constOut3 = str2num(pythonScriptOutputString(dataStringArray(3)+1:dataStringArray(4)-1));
constOut4 = str2num(pythonScriptOutputString(dataStringArray(4)+1:dataStringArray(5)-1));
constOut5 = str2num(pythonScriptOutputString(dataStringArray(5)+1:end));

When using an extrinsic function, the data type returned is of mxArray, which you cannot index into as the error message suggests. To work around this problem, you first need to initialise the variable(s) of interest to cast them to the right data type (e.g. double). See Working with mxArrays in the documentation for examples of how to do that.
The second part of the error message is a dimension. Without seeing the code of the function, the Simulink model and how the inputs/outputs of the function are defined, it's difficult to tell what's going on, but you need to make sure you have the correct size and data type defined in the Ports and Data manager.