Python速度测试-时差-毫秒-Python 实用宝典

# Python速度测试-时差-毫秒

## 问题：Python速度测试-时差-毫秒

``````from datetime import datetime

tstart = datetime.now()
print t1

# code to speed test

tend = datetime.now()
print t2
# what am I missing?
# I'd like to print the time diff here``````

What is the proper way to compare 2 times in Python in order to speed test a section of code? I tried reading the API docs. I'm not sure I understand the timedelta thing.

So far I have this code:

``````from datetime import datetime

tstart = datetime.now()
print t1

# code to speed test

tend = datetime.now()
print t2
# what am I missing?
# I'd like to print the time diff here
``````

## 回答 0

`datetime.timedelta` 只是两个日期时间之间的差...所以就像一段时间，以天/秒/微秒为单位

``````>>> import datetime
>>> a = datetime.datetime.now()
>>> b = datetime.datetime.now()
>>> c = b - a

>>> c
datetime.timedelta(0, 4, 316543)
>>> c.days
0
>>> c.seconds
4
>>> c.microseconds
316543``````

``````>>> c / 10
datetime.timedelta(0, 0, 431654)``````

`datetime.timedelta` is just the difference between two datetimes ... so it's like a period of time, in days / seconds / microseconds

``````>>> import datetime
>>> a = datetime.datetime.now()
>>> b = datetime.datetime.now()
>>> c = b - a

>>> c
datetime.timedelta(0, 4, 316543)
>>> c.days
0
>>> c.seconds
4
>>> c.microseconds
316543
``````

Be aware that `c.microseconds` only returns the microseconds portion of the timedelta! For timing purposes always use `c.total_seconds()`.

You can do all sorts of maths with datetime.timedelta, eg:

``````>>> c / 10
datetime.timedelta(0, 0, 431654)
``````

It might be more useful to look at CPU time instead of wallclock time though ... that's operating system dependant though ... under Unix-like systems, check out the 'time' command.

## 回答 1

``````>>> import datetime
>>> a = datetime.datetime.now()
>>> b = datetime.datetime.now()
>>> delta = b - a
>>> print delta
0:00:05.077263
>>> int(delta.total_seconds() * 1000) # milliseconds
5077``````

Since Python 2.7 there's the timedelta.total_seconds() method. So, to get the elapsed milliseconds:

``````>>> import datetime
>>> a = datetime.datetime.now()
>>> b = datetime.datetime.now()
>>> delta = b - a
>>> print delta
0:00:05.077263
>>> int(delta.total_seconds() * 1000) # milliseconds
5077
``````

## 回答 2

You might want to use the timeit module instead.

## 回答 3

``````import time

start = time.clock()
do_something()
end = time.clock()
print "%.2gs" % (end-start)``````

You could also use:

``````import time

start = time.clock()
do_something()
end = time.clock()
print "%.2gs" % (end-start)
``````

Or you could use the python profilers.

## 回答 4

``````import time
start = time.time()

##### your timed code here ... #####

print "Process time: " + (time.time() - start)``````

`time.time()`从纪元开始，您可以得到秒数。因为这是标准时间（以秒为单位），所以您可以简单地从结束时间中减去开始时间来获得处理时间（以秒为单位）。`time.clock()`对基准测试非常有用，但是如果您想知道过程花费了多长时间，我发现它毫无用处。例如，说“我的过程需要10秒”比说“我的过程需要10个处理器时钟单位”要直观得多。

``````>>> start = time.time(); sum([each**8.3 for each in range(1,100000)]) ; print (time.time() - start)
3.4001404476250935e+45
0.0637760162354
>>> start = time.clock(); sum([each**8.3 for each in range(1,100000)]) ; print (time.clock() - start)
3.4001404476250935e+45
0.05``````

``````>>> start = time.clock(); time.sleep(1) ; print "process time: " + (time.clock() - start)
process time: 0.0
>>> start = time.time(); time.sleep(1) ; print "process time: " + (time.time() - start)
process time: 1.00111794472``````

I know this is late, but I actually really like using:

``````import time
start = time.time()

##### your timed code here ... #####

print "Process time: " + (time.time() - start)
``````

`time.time()` gives you seconds since the epoch. Because this is a standardized time in seconds, you can simply subtract the start time from the end time to get the process time (in seconds). `time.clock()` is good for benchmarking, but I have found it kind of useless if you want to know how long your process took. For example, it's much more intuitive to say "my process takes 10 seconds" than it is to say "my process takes 10 processor clock units"

``````>>> start = time.time(); sum([each**8.3 for each in range(1,100000)]) ; print (time.time() - start)
3.4001404476250935e+45
0.0637760162354
>>> start = time.clock(); sum([each**8.3 for each in range(1,100000)]) ; print (time.clock() - start)
3.4001404476250935e+45
0.05
``````

In the first example above, you are shown a time of 0.05 for time.clock() vs 0.06377 for time.time()

``````>>> start = time.clock(); time.sleep(1) ; print "process time: " + (time.clock() - start)
process time: 0.0
>>> start = time.time(); time.sleep(1) ; print "process time: " + (time.time() - start)
process time: 1.00111794472
``````

In the second example, somehow the processor time shows "0" even though the process slept for a second. `time.time()` correctly shows a little more than 1 second.

## 回答 5

``````from datetime import datetime

tstart = datetime.now()

# code to speed test

tend = datetime.now()
print tend - tstart``````

The following code should display the time detla...

``````from datetime import datetime

tstart = datetime.now()

# code to speed test

tend = datetime.now()
print tend - tstart
``````

## 回答 6

``print tend - tstart``

You could simply print the difference:

``````print tend - tstart
``````

## 回答 7

``````from datetime import datetime

tstart = datetime.now()

# code to speed test

tend = datetime.now()
print tend - tstart``````

I am not a Python programmer, but I do know how to use Google and here's what I found: you use the "-" operator. To complete your code:

``````from datetime import datetime

tstart = datetime.now()

# code to speed test

tend = datetime.now()
print tend - tstart
``````

Additionally, it looks like you can use the strftime() function to format the timespan calculation in order to render the time however makes you happy.

## 回答 8

time.time（）/ datetime可以快速使用，但并不总是100％精确。出于这个原因，我喜欢使用其中一个std lib 分析器（尤其是hotshot）来找出问题所在。

time.time() / datetime is good for quick use, but is not always 100% precise. For that reason, I like to use one of the std lib profilers (especially hotshot) to find out what's what.

## 回答 9

You may want to look into the profile modules. You'll get a better read out of where your slowdowns are, and much of your work will be full-on automated.

## 回答 10

``````time_var = time_me(); # get a variable with the current timestamp

... run operation ...

time_me(time_var); # print the time difference (e.g. '5 seconds 821.12314 ms')``````

``````def time_me(*arg):
if len(arg) != 0:
elapsedTime = time.time() - arg[0];
#print(elapsedTime);
hours = math.floor(elapsedTime / (60*60))
elapsedTime = elapsedTime - hours * (60*60);
minutes = math.floor(elapsedTime / 60)
elapsedTime = elapsedTime - minutes * (60);
seconds = math.floor(elapsedTime);
elapsedTime = elapsedTime - seconds;
ms = elapsedTime * 1000;
if(hours != 0):
print ("%d hours %d minutes %d seconds" % (hours, minutes, seconds))
elif(minutes != 0):
print ("%d minutes %d seconds" % (minutes, seconds))
else :
print ("%d seconds %f ms" % (seconds, ms))
else:
#print ('does not exist. here you go.');
return time.time()``````

Here is a custom function that mimic's Matlab's/Octave's `tic` `toc` functions.

Example of use:

``````time_var = time_me(); # get a variable with the current timestamp

... run operation ...

time_me(time_var); # print the time difference (e.g. '5 seconds 821.12314 ms')
``````

Function :

``````def time_me(*arg):
if len(arg) != 0:
elapsedTime = time.time() - arg[0];
#print(elapsedTime);
hours = math.floor(elapsedTime / (60*60))
elapsedTime = elapsedTime - hours * (60*60);
minutes = math.floor(elapsedTime / 60)
elapsedTime = elapsedTime - minutes * (60);
seconds = math.floor(elapsedTime);
elapsedTime = elapsedTime - seconds;
ms = elapsedTime * 1000;
if(hours != 0):
print ("%d hours %d minutes %d seconds" % (hours, minutes, seconds))
elif(minutes != 0):
print ("%d minutes %d seconds" % (minutes, seconds))
else :
print ("%d seconds %f ms" % (seconds, ms))
else:
#print ('does not exist. here you go.');
return time.time()
``````

## 回答 11

``\$ python -mtimeit -s 'import module'``

You could use timeit like this to test a script named module.py

``````\$ python -mtimeit -s 'import module'
``````

## 回答 12

《箭头》：Python的更好日期和时间

``````import arrow
start_time = arrow.utcnow()
end_time = arrow.utcnow()
(end_time - start_time).total_seconds()  # senconds
(end_time - start_time).total_seconds() * 1000  # milliseconds``````

Arrow: Better dates & times for Python

``````import arrow
start_time = arrow.utcnow()
end_time = arrow.utcnow()
(end_time - start_time).total_seconds()  # senconds
(end_time - start_time).total_seconds() * 1000  # milliseconds
``````