system.tag.readBlocking

This function is used in Python Scripting.

Description

Reads the value of the tags at the given paths. Will "block" until the read operation is complete or times out. Meaning, execution of the calling script will pause until this function finishes. This is useful in cases where the tag read must complete before further lines in the same script should execute.

Client Permission Restrictions

This scripting function has no Client Permission restrictions.

Syntax

system.tag.readBlocking(tagPaths, [timeout])

Parameters

Type	Parameter	Description
String or List[String]	tagPaths	Either a string of a single tag path, or a list of strings tag paths to read from. If no property is specified in a path, the Value property is assumed.
Integer	timeout	How long to wait in milliseconds before the read operation times out. This parameter is optional, and defaults to 45000 milliseconds if not specified. [optional]

Returns

List - A list of QualifiedValue objects corresponding to the tag paths. See Scripting Object Reference.

Scope

Gateway, Vision Client, Perspective Session

Code Examples

Example #1 - Read From Multiple Tags

# Specify the paths.
paths = ["[default]Folder/Tag_A","[default]Folder/Tag_B"]
 
# Send the reads off.
values = system.tag.readBlocking(paths)
 
# Here we can examine each value.
for i in range(len(values)):
    print "Tag at Path: %s\n Had a value of %s" % (paths[i], values[i].value)

Example #2 - Read From a Single Tag

# Specify the paths.
path = ["[default]Folder/Tag_A"]
 
# Send the reads off.
# Function returns a list of qualified values, one qualified value for every tag path we are reading
qualifiedValues= system.tag.readBlocking(path)
value = qualifiedValues[0] # extract the qualified value from this list, there should only be 1 because we are reading a single tag value
 
print value.value # prints out the value of the Tag A
print value.quality # prints out the quality of Tag A
print value.timestamp # prints out the timestamp of Tag A's value