import ctypes
import six
from collections.abc import Sequence
from nidaqmx._lib import lib_importer, ctypes_byte_str
from nidaqmx._task_modules.channels.channel import Channel
from nidaqmx.errors import (
check_for_error, is_string_buffer_too_small, is_array_buffer_too_small,
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):
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:
nidaqmx._task_modules.channels.channel.Channel:
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:`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, '')
@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'))