{"id":628,"date":"2018-04-07T04:46:44","date_gmt":"2018-04-07T04:46:44","guid":{"rendered":"http:\/\/www.afternerd.com\/blog\/?p=628"},"modified":"2019-01-13T03:29:02","modified_gmt":"2019-01-13T03:29:02","slug":"timeit-multiple-lines","status":"publish","type":"post","link":"https:\/\/www.afternerd.com\/blog\/timeit-multiple-lines\/","title":{"rendered":"Python: How to use the ‘timeit’ module for multiple lines?"},"content":{"rendered":"

It is very useful to time small snippets of python code.<\/p>\n

For example, you might want to do that\u00a0to debug performance bottlenecks or to compare the efficiencies of different ways to perform a task.<\/p>\n

The timeit<\/span>\u00a0module is a handy python module that allows you to do just that.<\/p>\n

Even though it is pretty straight forward to use this module to time one-line statements, you might find it a little tricky to time multiple-line statements.<\/p>\n

In this article, I will teach you how to use this awesome python module to time multiple lines.<\/p>\n

But before we dive into how to do that, let’s revisit the different ways you can use the timeit<\/span> module.<\/p>\n

for example, say you want to time this statement<\/p>\n

L = [2 ** n for n in range(10)]<\/code><\/pre>\n
There are two ways you can do this<\/p>\n
First: From python code<\/h3>\n
In your python code, you can jump import the module and use the timeit method.<\/p>\n
>>> import timeit\r\n>>> timeit.timeit('L = [2 ** n for n in range(10)]')\r\n3.0072080040117726<\/code><\/pre>\n
Second: From the command line interface<\/h3>\n
Another way is to just invoke the timeit module from the shell like this<\/p>\n
$ python3 -m timeit 'L = [2 ** n for n in range(10)]'\r\n100000 loops, best of 3: 2.99 usec per loop<\/code><\/pre>\n
Seems pretty straightforward, right?<\/p>\n
Now how can you use the timeit<\/span> module to time a snippet of python code that spans multiple lines?<\/p>\n
Let’s discuss how you can do that from python code and from the command line interface.<\/p>\n
Timing multiple lines in python code<\/h2>\n
Timing multiple-line code snippets frome python code is very simple<\/p>\n
Same indentation<\/h3>\n
The easiest way to time multiple lines having the same indentation is to use semicolons to separate the lines.<\/p>\n
For example, say you want to time the following snippet.<\/p>\n
x = 2\r\nL = [x ** n for n in range(10)]<\/code><\/pre>\n
your code will look like this<\/p>\n
>>> import timeit\r\n>>> timeit.timeit('x = 2; L = [x ** n for n in range(10)]')\r\n3.0759821450337768<\/code><\/pre>\n
Easy peasy!<\/p>\n
But what if your code have different indentations?<\/p>\n
Different indentations<\/h3>\n
The easiest way to handle different indentations is to to define your code snippet as a string first using triple quotes.<\/p>\n
The reason why you should use triple quotes is because it allows you to\u00a0define strings that can span multiple lines<\/a>.<\/p>\n
For example, you can do something like this<\/p>\n
import timeit\r\ns = \"\"\"\\\r\nL = []\r\nfor n in range(10):\r\n    L.append(2 ** n)\"\"\"\r\nt = timeit.timeit(s)<\/code><\/pre>\n
Prefect, now let’s discuss how you can do the same thing but from the command line interface.<\/p>\n
Timing multiple lines in the command-line interface<\/h2>\n
Same indentation<\/h3>\n
For multiple lines that have the same indentation, you can still use semicolons like you did in the previous case.<\/p>\n
$ python3 -m timeit 'x = 2; L = [x ** n for n in range(10)]'\r\n100000 loops, best of 3: 3.07 usec per loop<\/code><\/pre>\n
But this is not the only way.<\/p>\n
You can also specify each line as a separate statement argument like this<\/p>\n
$ python3 -m timeit 'x = 2' 'L = [x ** n for n in range(10)]'\r\n100000 loops, best of 3: 3.03 usec per loop<\/code><\/pre>\n
This separation of statements into different arguments allows us to specify indentations as well.<\/p>\n
Let’s see how.<\/p>\n
Different indentations<\/h3>\n
For multiple lines with different indentations, you specify each line as a separate argument and you also preserve the leading spaces.<\/p>\n
For example, to time<\/p>\n
L = []\r\nfor n in range(10):\r\n    L.append(2 ** n)<\/code><\/pre>\n
you can do something like this:<\/p>\n
$ python3 -m timeit \\\r\n'L = []' 'for n in range(10):' '    L.append(2 ** n)'\r\n100000 loops, best of 3: 3.47 usec per loop<\/code><\/pre>\n
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