How do I add additional behavior before and after the Python function is executed

Let's start with a small program that measures the amount of time it takes. Here's an example of a previous solution

from functools import wraps, partial
from time import time

def timing(func=None, frequencies=1):
 if func is None:
  # print("+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_time = time()
  print(' Running time: {:.6f}s . '.format(end_time-start_time))
  return result

 return _wrapper


@timing
def run():
 l = []
 for i in range(5000000):
  l.extend([i])
 return len(l)

It runs as follows:

In [4]: run()
 Running time: 2.383398s . 
Out[4]: 5000000

(those who like to get to the bottom can remove the comments and think about what output to expect).

Today I came across Python's context manager ( Context Manager ), and it turns out to be pretty good, too with The statement is closely related, actually before 1 straight did not care.

from time import time

def 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(' Running time: {:.6f}s . '.format(self.end_time - self.start_time))

with ElapsedTime():
 run2()

conclusion

After a brief look at 1 point of official documentation, context management is still a bit much. So far, Python has not been easy. Say simple, just you are not up to date with The Times, master is the old 3 plank axe just. Therefore, the knowledge needs to be constantly updated, in order to make up for their own blind spots, the above is all the content of this article, I hope you can study or work to bring 1 definite help.