How to add extra behavior before and after a Python function is executed

First look at a small program, this is the measurement of the time spent in the program, the following is the previous solution example

From Functools import wraps, Partialfrom time import timedef timing (Func=none, Frequencies=1): If Func is None:  # Prin T ("+none")  return Partial (timing, frequencies=frequencies) # Else:  # print ("-none") @wraps (func) def _wrapper ( *args, **kwargs):  start_time = time () for  T in range (frequencies):   result = Func (*args, **kwargs)  End_ Times = time ()  print (' run elapsed: {:. 6f}s. '. Format (end_time-start_time))  return result return _wrapper@timingdef run (): L = [] for I in range (5000000):  L.E Xtend ([i]) return Len (L)

Run as follows:

In [4]: Run () Elapsed time: 2.383398s. OUT[4]: 5000000

(like to be inquisitive, you can get rid of comments and think about what kind of output is expected).

Today I inadvertently see the context manager of Python ( Context Manager ), found also very good, in fact, this with is closely related to the statement, unexpectedly has never cared.

From time import Timedef run2 (): L = [] for I in range (5000000):  l.extend ([i]) return Len (L) class ElapsedTime (): def _ _enter__ (self):  Self.start_time = time ()  return self def __exit__ (self, exception_type, Exception_value, Traceback):  self.end_time = time ()  print (' runtime elapsed: {:. 6f}s. '. Format (self.end_time-self.start_time)) with ElapsedTime (): Run2 ()

Summarize

A little bit of official documentation, context management or a lot of content. Python has evolved into the present, but it's not easy. Say simple, but you are not enough to keep pace with the times, master is old-fashioned kick just. Therefore, knowledge needs to be constantly updated to make up for their blind spots, the above is the whole content of this article, I hope we can learn or work to bring some help.

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