contextlib.closing

from contextlib import closing
import serial

##############################################
              Better example
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# https://docs.python.org/2.7/library/contextlib.html
# https://docs.python.org/3.5/library/contextlib.html

with closing(serial.Serial('/dev/ttyUSB0', baudrate=11520)) as ser:
    print(ser.inWaiting())
    # the function closing calls the method
    # close of the wrapped object when leaving
    # the context

# Here is the serial connection already closed :-)