from collections.abc import Sequence
from nidaqmx._task_modules.channels.channel import Channel
from nidaqmx.errors import DaqError
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, interpreter):
"""
Do not construct this object directly; instead, construct a nidaqmx.Task and use the appropriate property, such as task.ai_channels.
"""
self._handle = task_handle
self._interpreter = interpreter
def __contains__(self, item):
channel_names = self.channel_names
if isinstance(item, str):
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:
nidaqmx._task_modules.channels.channel.Channel:
Indicates a channel object representing the subset of virtual
channels indexed.
"""
if isinstance(index, int):
channel_names = self.channel_names[index]
elif isinstance(index, slice):
channel_names = flatten_channel_string(self.channel_names[index])
elif isinstance(index, str):
channel_names = index
else:
raise DaqError(
'Invalid index type "{}" used to access channels.'
.format(type(index)), DAQmxErrors.UNKNOWN)
if channel_names:
return Channel._factory(self._handle, channel_names, self._interpreter)
else:
raise DaqError(
'You cannot specify an empty index when indexing channels.\n'
'Index used: {}'.format(index), DAQmxErrors.UNKNOWN)
def __hash__(self):
return self._interpreter.hash_task_handle(self._handle)
def __iter__(self):
for channel_name in self.channel_names:
yield Channel._factory(self._handle, channel_name, self._interpreter)
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, self._interpreter)
@property
def all(self):
"""
:class:`nidaqmx._task_modules.channels.channel.Channel`:
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, '', self._interpreter)
@property
def channel_names(self):
"""
List[str]: Specifies the entire list of virtual channels on this
channel collection.
"""
val = self._interpreter.get_task_attribute_string(self._handle, 0x1273)
return unflatten_channel_string(val)