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This article mainly explains "what are the tricks and skills of Python". The content of the explanation is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "what are the tricks and skills of Python"?

1. Use Python 3

Python officially announced that Python 2 will not be supported officially from January 1, 2020. This article has a bunch of examples that can only work in Python 3. If your version is still Python 2.7, upgrade to Python 3.x.

two。 Check the minimum required Python version

You can check the Python version in your code to make sure that you are not running the script with an incompatible version. Use the following simple checks:

Import sys# checks the python version and exits the program def check_version (): v = sys.version_info# print (v) # sys.version_info (major=3, minor=6, micro=5, releaselevel='final', serial=0) if v.major = = 3 and v.minor > = 5:returnprint ('Your current python is% d.d. Please use Python 3.6.'% (v.major, v.minor)) exit (1) 3. Use IPython

IPython is an enhanced shell tool. You can do code completion automatically, but there are a lot of commands, and I like all the built-in magic commands. For example:

% cd-change the current working directory

% edit-Open the editor and execute the code you typed after closing the editor

% env-displays the current environment variable

% pip install [pkgs]-install the package without leaving the interactive shell

% time and% timeit- regularly execute Python code

Another useful feature is to reference the output of previous commands. Inputs and outputs are actual objects. You can use the output of the third command using Out [3].

Install IPython using the following command:

Pip3 install ipython

4. List (list) understanding

List understanding can be used instead of ugly for loops to populate lists. The basic syntax for list understanding is: [expression for item in list if conditional]

A very simple example of populating a list with a sequence of numbers:

[i for i in range (10)]

And because expressions can be used, you can also do some mathematical operations and even call external functions.

Finally, you can use if to filter the list. In this case, we keep only values that are divisible by 2:

[i for i in range (10) if I% 2 percent 0]

5. Check the memory usage of an object

With sys.getsizeof (), you can check the memory usage of the object.

6. Return multiple values

Functions in Python can return multiple variables without the need for dictionaries, lists or classes.

This is fine for a limited number of return values. But anything with more than three values should be put into the class.

7. Use the data class

Starting with Python version 3.7, Python provides the data class. It has several advantages over regular classes or other alternatives, such as returning multiple values or dictionaries:

Data classes require the least amount of code

You can compare the data class because it _ _ eq__ has been implemented for you

You can also easily print a data class for debugging, because it _ _ repr__ has also been implemented

The data class requires a type hint, which reduces the chance of errors

8. Local variable exchange

An ingenious trick can save a few lines of code.

A _

9. Merge dictionaries (Python 3.5 +)

Starting with Python 3.5, it becomes easier to merge dictionaries:

If the keys (key) overlap, the keys (key) in the first dictionary are overwritten.

10. The case of the first letter

Use the capitalize () function to uppercase the first letter of the string and lowercase the rest.

"welcome" .capitalize ()

11. Split a string into a list

You can split the string into a list of strings. In this case, we split the space characters:

List ("welcome")

twelve。 Create a string from a list of strings

And vice versa, starting with the previous trick, create a string from the list and add a space character between each word:

">

13. Emoji

It will be impressive or ostracized, depending on who is looking. What's more, it can come in handy, especially when analyzing social media data.

First, install the emoji module:

Pip3 install emoji

After installing this program, you can do the following:

14. List (list) slice

The basic syntax of list slices is: a [start: stop:step]

Start,stop and step are optional. If it is left empty, the default is:

0 is start

The end of the string end

Step defaults to 1

Here are some examples:

A = [0,1,2,3,4,5,6,7,8,9] a [2: 5:2] 15. Reverse strings and lists

You can use the slice symbol from the top to reverse the string or list. By using step=-1, reverse the element:

A [:-1] 16. Show kittens

I finally found a good excuse to show kittens in one of the articles! However, you may use it to display graphics, and so on. First, install Pillow (https://pypi.org/project/Pillow/), a branch of the Python image library:

Pip3 install Pillow

Now, download the image to a file called "kitchess.jpg":

You can operate directly from IPython:

Pillow can not only display images, but also do more things. It can be analyzed, resized, filtered, enhanced, deformed, etc. For all features, refer to the documentation

17. Use map ()

One of the built-in functions of Python is called map (). The syntax for map () is:

Map (function, something_iterable)

Therefore, you provide it with the functions to perform and some of the functions to be performed. This can be anything that can be iterated. In the following example, I will use a list a = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9].

List (map (lambda x: Xue1jia a))

Take a look at your own code and see if map () can be used somewhere instead of a loop!

18. Get a unique element from a list or string

By using the set () function to create a collection, you can get all the unique elements from a list or similar list of objects a = [1meme 1meme 2meme 3mem4mem4].

Set (a) 19. Find the values that appear most frequently

To find the values that appear most frequently in a list or string:

Test= [1,1,2,3,4,4,4,4]

Do you know why this works? Please figure it out for yourself before you go on reading. You didn't try, did you? Anyway, I'll tell you:

Max () returns the maximum value in the list. The key parameter takes a single parameter function to customize the sort order, in this case test.count. This function applies to each project on the iterator.

Test.count is the built-in function of list. It accepts a parameter and calculates the number of occurrences of that parameter. So test.count (1) will return 2st test. count (4) will return 4.

Set (test) returns all the unique values of the test, so {1, 2, 3, 4} so what we do in a single line of code is to get all the unique values of test, that is, {1, 2, 3, 4}. Next, max applies the list.count function to them and returns the maximum value.

20. Create a progress bar

You can create your own progress bar, which is interesting. But using progress packages is faster:

Pip3 install progress

Now you can easily create a progress bar.

21. Use _ in interactive shell

You can use the underscore operator to get the result of the last expression, for example, in IPython, it looks like:

In [1]: 3 * 3Out [1]: 9In [2]: _ + 3Out [2]: 12

This can also be used in Python Shell. In addition, IPython shell allows you to use out [n] to get the value of an expression in In [n] for example, Out [1] in the above example, _ can get the number 9.

twenty-two。 Quickly create a Web server

You can quickly start the Web server to provide the contents of the current directory:

Python3-m http.server

This is useful if you want to share something with colleagues or want to test a simple HTML site.

23. Multiline string

Although you can use three quotes to include multiple lines of strings in your code, this is not ideal. Everything placed between the three quotation marks becomes a string, including the format, as shown below. I prefer the second method, which concatenates multiple lines together and formats the code well. The only drawback is that you need to explicitly add newline characters.

24. Ternary operator for conditional assignment

This is another way to make your code more concise while keeping it readable:

[on_true] if [expression] else [on_false]

For example:

X = "Success!" If (y = = 2) else "Failed!" 25. Count

You can use Counter in the collection library to get a dictionary that contains the count of all unique elements in the list:

From collections import Countera= [1,1,2,3,4,4] Counter (a) 26. Links to compare operators

You can link the comparison operator in Python to create more readable and concise code:

twenty-seven。 Add some colors

twenty-eight。 Processing date

Python-dateutil module (https://pypi.org/project/python-dateutil/) provides a powerful extension to the standard datetime module. Install in the following ways:

Pip3 install python-dateutil

You can do a lot of cool things with this library. I will limit the example to one that I find particularly useful: fuzzy parsing of dates in log files, and so on.

Just remember: where the regular Python date-time function ends, python-dateutil appears!

twenty-nine。 Integer division

In Python 2, the division operator (/) defaults to integer division unless one of the operands is a floating-point number. Therefore, you have the following behavior:

# Python 2 5max 2 = 2 5 / 2 0 = 2 5

In Python 3, the division operator defaults to floating point division, and the / / operator has become an integer division. In this way we get:

# Python 3 5Compact 2 = 2.55 / / 2 = 230. Character set detection using chardet

You can use the chardet module to detect the character set of a file. This is useful when analyzing large amounts of random text. Installation method:

Pip install chardet

Now you have an extra command-line tool called chardetect, which can be used like this

Chardetect somefile.txtsomefile.txt: ascii with confidence 1.0Thank you for your reading. These are the contents of "what are the tricks and skills of Python". After the study of this article, I believe you have a deeper understanding of what the tricks and skills of Python are, and the specific use needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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