Assuming your files are named 1.png, 2.png, 3.png …, you can load the texture with:
from panda3d.core import TexturePool
tex_array = TexturePool.load2dTextureArray("#.png")(There are further options like also including mipmaps and so on, also see [url]Texture Arrays])
If you want to use the texture with the shader generator, you will have to use 3-component texture coordinates instead of 2-component - basically the third component is the index in the texture array. For that you will have to create a custom GeomVertexFormat I believe.
If you want to use the texture in a custom shader, you would do:
uniform sampler2DArray my_tex;
...
vec4 color = texture(my_tex, vec3(uv_coordinate.xy, layer_index)));