Source code for nidaqmx._task_modules.channel_collection

import ctypes
import six
from import Sequence

from nidaqmx._lib import lib_importer, ctypes_byte_str
from import Channel
from nidaqmx.errors import (
    check_for_error, is_string_buffer_too_small, is_array_buffer_too_small,
from nidaqmx.error_codes import DAQmxErrors
from nidaqmx.utils import unflatten_channel_string, flatten_channel_string

[docs]class ChannelCollection(Sequence): """ Contains the collection of channels for a DAQmx Task. This class defines methods that implements a container object. """ def __init__(self, task_handle): self._handle = task_handle def __contains__(self, item): channel_names = self.channel_names if isinstance(item, six.string_types): items = unflatten_channel_string(item) elif isinstance(item, Channel): items = item.channel_names return all([item in channel_names for item in items]) def __eq__(self, other): if isinstance(other, self.__class__): return self._handle == other._handle return False def __getitem__(self, index): """ Indexes a subset of virtual channels on this channel collection. Args: index: The value of the index. The following index types are supported: - str: Name of the virtual channel. You also can specify a string that contains a list or range of names to this input. If you have a list of names, use the DAQmx Flatten Channel String function to convert the list to a string. - int: Index/position of the virtual channel in the collection. - slice: Range of the indexes/positions of virtual channels in the collection. Returns: Indicates a channel object representing the subset of virtual channels indexed. """ if isinstance(index, six.integer_types): channel_names = self.channel_names[index] elif isinstance(index, slice): channel_names = flatten_channel_string(self.channel_names[index]) elif isinstance(index, six.string_types): channel_names = index else: raise DaqError( 'Invalid index type "{0}" used to access channels.' .format(type(index)), DAQmxErrors.UNKNOWN) if channel_names: return Channel._factory(self._handle, channel_names) else: raise DaqError( 'You cannot specify an empty index when indexing channels.\n' 'Index used: {0}'.format(index), DAQmxErrors.UNKNOWN) def __hash__(self): return hash(self._handle.value) def __iter__(self): for channel_name in self.channel_names: yield Channel._factory(self._handle, channel_name) def __len__(self): return len(self.channel_names) def __ne__(self, other): return not self.__eq__(other) def __reversed__(self): channel_names = self.channel_names channel_names.reverse() for channel_name in channel_names: yield Channel._factory(self._handle, channel_name) @property def all(self): """ :class:``: Specifies a channel object that represents the entire list of virtual channels on this channel collection. """ # Passing a blank string means all channels. return Channel._factory(self._handle, '') @property def channel_names(self): """ List[str]: Specifies the entire list of virtual channels on this channel collection. """ cfunc = lib_importer.windll.DAQmxGetTaskChannels if cfunc.argtypes is None: with cfunc.arglock: if cfunc.argtypes is None: cfunc.argtypes = [ lib_importer.task_handle, ctypes.c_char_p, ctypes.c_uint] temp_size = 0 while True: val = ctypes.create_string_buffer(temp_size) size_or_code = cfunc( self._handle, val, temp_size) if is_string_buffer_too_small(size_or_code): # Buffer size must have changed between calls; check again. temp_size = 0 elif size_or_code > 0 and temp_size == 0: # Buffer size obtained, use to retrieve data. temp_size = size_or_code else: break check_for_error(size_or_code) return unflatten_channel_string(val.value.decode('ascii'))