How to obtain a Thread id in Python?

user_11677 0
Viewed 311640

I have a multi-threading Python program, and a utility function, writeLog(message), that writes out a timestamp followed by the message. Unfortunately, the resultant log file gives no indication of which thread is generating which message.

I would like writeLog() to be able to add something to the message to identify which thread is calling it. Obviously I could just make the threads pass this information in, but that would be a lot more work. Is there some thread equivalent of os.getpid() that I could use?

python-logging python-multithreading multithreading python
8 Answers
user_63720

Using the logging module you can automatically add the current thread identifier in each log entry. Just use one of these LogRecord mapping keys in your logger format string:

%(thread)d : Thread ID (if available).

%(threadName)s : Thread name (if available).

and set up your default handler with it:

logging.basicConfig(format="%(threadName)s:%(message)s")
user_51810
user_85758470

You can get the ident of the current running thread. The ident could be reused for other threads, if the current thread ends.

When you crate an instance of Thread, a name is given implicit to the thread, which is the pattern: Thread-number

The name has no meaning and the name don't have to be unique. The ident of all running threads is unique.

import threading


def worker():
    print(threading.current_thread().name)
    print(threading.get_ident())


threading.Thread(target=worker).start()
threading.Thread(target=worker, name='foo').start()

The function threading.current_thread() returns the current running thread. This object holds the whole information of the thread.

user_28173540

I saw examples of thread IDs like this:

class myThread(threading.Thread):
    def __init__(self, threadID, name, counter):
        self.threadID = threadID
        ...

The threading module docs lists name attribute as well:

...

A thread has a name. 
The name can be passed to the constructor, 
and read or changed through the name attribute.

...

Thread.name

A string used for identification purposes only. 
It has no semantics. Multiple threads may
be given the same name. The initial name is set by the constructor.
user_893910
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