24 useful Python tips

This article is published in my official account 『 data STUDIO』：24 A good one Python Practical skills

Python Is the most popular in the world 、 One of the most popular programming languages , Yes, there are many reasons .

• It's easy to learn
• There are super many functions
• It has a large number of modules and Libraries

As a data worker , We use it every day Python Handle most of the work . In the process , We will continue to learn some useful skills and tricks .

ad locum , I tried to A - Z Share some of these tips in the beginning format , And these methods are briefly introduced in this paper , If you are interested in one or more of them , You can check the official documents through the references at the end of the article . I hope it can help you .

all or any

Python One of the many reasons why languages are so popular , Because it has good readability and expressiveness .

People often joke that Python yes Executable pseudocode . When you can write code like this , It's hard to refute .

x = [True, True, False]
if any(x):
    print(" At least one True")
if all(x):
    print(" Is full of True")
if any(x) and not all(x):
    print(" At least one True And a False")
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bashplotlib

Have you ever thought about drawing graphics in the console ？

Bashplotlib It's a Python library , He can help us on the command line ( A rough environment ) Draw data in .

#  Module installation 
pip install bashplotlib
#  Draw examples 
import numpy as np
from bashplotlib.histpgram import plot_hist
arr = np.ramdom.normal(size=1000, loc=0, scale=1)
plot_hist(arr, bincount=50)
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collections

Python There are some great default data types , But sometimes their behavior doesn't exactly meet your expectations .

Fortunately, ,Python The standard library provides collections modular . This convenient add-on provides you with more data types .

from collections import OrderedDict, Counter
#  Remember the order in which keys are added ！
x = OrderedDict(a=1, b=2, c=3)
#  Count the frequency of each character 
y = Counter("Hello World!")
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dir

Have you ever thought about how to check Python Object and see what properties it has ？ Enter... On the command line ：

dir() 
dir("Hello World") 
dir(dir)
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When running interactively Python And dynamically explore the objects and modules you are using , This can be a very useful feature . Read more here functions Related content .

emoji

emoji It is a visual emotional symbol used in wireless communication in Japan , Drawing refers to drawing , Words refer to characters , Can be used to represent a variety of expressions , A smiling face means a smile 、 Cake means food, etc . On Chinese mainland ,emoji Is often called “ Little yellow face ”, Or call it emoji.

#  Install the module 
pip install emoji
#  Make a try 
from emoji import emojize
print(emojize(":thumbs_up:"))
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from __future__ import

Python One of the results of popularity , There are always new versions under development . The new version means new features —— Unless your version is out of date .

But don't worry . Use this __future__ modular Can help you use Python Future version import function . Literally , It's like time travel 、 Magic or something .

from __future__ import print_function
print("Hello World!")
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geogy

Geography , This is a challenging area for most programmers . When getting geographic information or drawing maps , There will be many problems . This geopy modular Make geography related content very easy .

pip install geopy
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It abstracts a series of different geocoding services API Come to work . Through it , You can get the full street address of a place 、 latitude 、 Longitude and even altitude .

There is also a useful distance class . It calculates the distance between two positions in your preferred unit of measurement .

from geopy import GoogleV3
place = "221b Baker Street, London"
location = GoogleV3().geocode(place)
print(location.address)
print(location.location)
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howdoi

When you use terminal When programming the terminal , By having a problem in StackOverflow Search for answers on , After that, it will return to the terminal to continue programming , Sometimes you don't remember the solution you found before , You need to review StackOverflow, But I don't want to leave the terminal , Then you need to use this useful command line tool howdoi.

pip install howdoi
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Whatever problems you have , You can ask it , It will try its best to reply .

howdoi vertical align css
howdoi for loop in java
howdoi undo commits in git
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But please pay attention to —— It will be from StackOverflow Grab the code from the best answer . It may not always provide the most useful information ......

howdoi exit vim
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inspect

Python Of inspect modular Perfect for understanding what's going on behind the scenes . You can even call its own methods ！

The following code example inspect.getsource() For printing your own source code . inspect.getmodule() It is also used to print the module that defines it .

The last line of code prints its own line number .

import inspect
print(inspect.getsource(inspect.getsource))
print(inspect.getmodule(inspect.getmodule))
print(inspect.currentframe().f_lineno)
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Of course , Except for these trivial uses ,inspect Modules can prove useful for understanding what your code is doing . You can also use it to write self documenting code .

Jedi

Jedi Library is an autocomplete and code analysis library . It makes writing code faster 、 More efficient .

Unless you're developing your own IDE, Otherwise you may use Jedi I'm interested in being an editor plug-in . Fortunately, , There are already loads available ！

**kwargs

When learning any language , There will be many milestones . Use Python And understand the mysterious **kwargs Grammar may count as an important milestone .

Double asterisk in front of dictionary object **kwargs Allows you to pass the contents of the dictionary as named parameters to the function .

The key of the dictionary is the parameter name , Value is the value passed to the function . You don't even need to call it kwargs！

dictionary = {"a": 1, "b": 2}
def someFunction(a, b):
    print(a + b)
    return
#  These do the same thing :
someFunction(**dictionary)
someFunction(a=1, b=2)
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When you want to write a function that can handle undefined named parameters , It's very useful .

list (list) The derived type

About Python Programming , One of my favorite things is its List derivation .

These expressions make it easy to write very smooth code , Almost like natural language .

numbers = [1,2,3,4,5,6,7]
evens = [x for x in numbers if x % 2 is 0]
odds = [y for y in numbers if y not in evens]
cities = ['London', 'Dublin', 'Oslo']

def visit(city):
    print("Welcome to "+city)
    
for city in cities:
    visit(city)
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map

Python Support functional programming with many built-in features . The most useful map() One of the functions is the function —— Especially with lambda function When used in combination .

x = [1, 2, 3] 
y = map(lambda x : x + 1, x)
#  Print out  [2,3,4]
print(list(y))
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In the example above ,map() Put a simple lambda Function applied to x. It returns a mapping object , The object can be converted into some iteratable objects , For example, list or tuple .

newspaper3k

If you haven't seen it yet , Then be ready to be Python newspaper module The module shocked to . It enables you to retrieve news articles and related metadata from a series of leading international publications . You can retrieve images 、 Text and author's name . It even has some Built in NLP function .

therefore , If you are considering using in your next project BeautifulSoup Or something else DIY Web crawling Library , Using this module can save you a lot of time and energy .

pip install newspaper3k
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Operator overloading

Python Provide right Operator overloaded Support , This is one of the terms that makes you sound like a legitimate computer scientist .

This is actually a simple concept . Have you ever thought about why Python Allow you to use + Operator to add numbers and connection strings ？ This is what operator overloading does .

You can define how to use... In your own specific way Python The object of the standard operator symbol . And you can use them in the context of the object you are using .

class Thing:
    def __init__(self, value):
        self.__value = value
    def __gt__(self, other):
        return self.__value > other.__value
    def __lt__(self, other):
        return self.__value < other.__value
something = Thing(100)
nothing = Thing(0)
# True
something > nothing
# False
something < nothing
# Error
something + nothing
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pprint

Python Default print The function does its job . But if you try to use print Function prints out any large nested objects , The result is rather ugly . The beautiful printing module of this standard library pprint You can print out complex structured objects in an easy to read format .

This is anything that uses non trivial data structures Python A must-have for developers .

import requests
import pprint
url = 'https://randomuser.me/api/?results=1'
users = requests.get(url).json()
pprint.pprint(users)
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Queue

Python Standard library Queue The module implementation supports multithreading . This module allows you to implement queue data structures . These are data structures that allow you to add and retrieve entries according to specific rules .

“ fifo ”（FIFO） Queues allow you to retrieve objects in the order they are added .“ Last in, first out ”(LIFO) Queues allow you to access recently added objects first .

Last , Priority queues allow you to retrieve objects according to their sort order .

This is a how in Python Queue is used in Queue Examples of multithreaded programming .

__repr__

stay Python When a class or object is defined in , Provides an... That represents the object as a string “ official ” This method is very useful . for example ：

>>> file = open('file.txt', 'r') 
>>> print(file) 
<open file 'file.txt', mode 'r' at 0x10d30aaf0>
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This makes it easier to debug code . Add it to your class definition , As shown below ：

class someClass: 
    def __repr__(self): 
        return "<some description here>"
someInstance = someClass()
#  Print  <some description here>
print(someInstance)
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sh

Python It's a great scripting language . Sometimes standard os and subprocess Ku may have a headache .

The SH library Allows you to call any program like a normal function —— Useful for automating workflows and tasks .

import sh
sh.pwd()
sh.mkdir('new_folder')
sh.touch('new_file.txt')
sh.whoami()
sh.echo('This is great!')
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Type hints

Python It is a dynamically typed language . Defining variables 、 function 、 Class does not need to specify the data type . This allows fast development time . however , Nothing is more annoying than runtime errors caused by simple input problems .

from Python 3.5 Start , You can choose to provide type hints when defining functions .

def addTwo(x : Int) -> Int:
    return x + 2
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You can also define type aliases .

from typing import List
Vector = List[float]
Matrix = List[Vector]
def addMatrix(a : Matrix, b : Matrix) -> Matrix:
  result = []
  for i,row in enumerate(a):
    result_row =[]
    for j, col in enumerate(row):
      result_row += [a[i][j] + b[i][j]]
    result += [result_row]
  return result
x = [[1.0, 0.0], [0.0, 1.0]]
y = [[2.0, 1.0], [0.0, -2.0]]
z = addMatrix(x, y)
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Although not mandatory , But type annotations can make your code easier to understand .

They also allow you to use type checking tools , Catch those stray before running TypeError. If you are dealing with large 、 Complex projects , It's very useful ！

uuid

adopt Python Standard library uuid modular Generate universal unique ID（ or “UUID”） A quick and simple method .

import uuid
user_id = uuid.uuid4()
print(user_id)
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This will create a random 128 Digit number , That number is almost certainly unique . in fact , Can generate more than 2¹²² It's possible UUID. This is more than five decimal （ or 5,000,000,000,000,000,000,000,000,000,000,000,000）.

The probability of finding duplicates in a given set is very low . Even if there are a trillion UUID, The possibility of repetition is also far less than one in a billion .

Virtual environments

You may be in multiple... At the same time Python Work on projects . Unfortunately , Sometimes two projects will depend on different versions of the same dependency . What did you install on your system ?

Fortunately, ,Python Support for A virtual environment So you can have the best of both worlds . From the command line ：

python -m venv my-project 
source my-project/bin/activate 
pip install all-the-modules
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Now? , You can run on the same machine Python Stand alone version and installation of .

wikipedia

Wikipedia has a great API, It allows users to programmatically access unparalleled and completely free knowledge and information . stay wikipedia modular Make access to the API Very convenient .

import wikipedia
result = wikipedia.page('freeCodeCamp')
print(result.summary)
for link in result.links:
    print(link)
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Just like the real site , The module provides multilingual support 、 Page disambiguation 、 Random page search , There's even one donate() Method .

xkcd

Humor is Python A key feature of language , It is based on English comedy skits Python Flying Circus Named .Python Many official documents cite the program's most famous sketches . however ,Python Humor is not limited to documents . Try running the following line ：

import antigravity
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YAML

YAML refer to “ Unmarked language ” . It's a data format language , yes JSON Superset .

And JSON Different , It can store more complex objects and reference its own elements . You can also write notes , Make it especially suitable for writing configuration files . The PyYAML modular You can use YAML Use Python.

Install and then import into your project ：

pip install pyyaml

import yaml
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PyYAML Allows you to store... Of any data type Python object , And any instances of user-defined classes .

zip

The finale is also a great module . Have you ever encountered the need to form a dictionary from two lists ？

keys = ['a', 'b', 'c']
vals = [1, 2, 3]
zipped = dict(zip(keys, vals))
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The zip() Built in functions require a series of iteratable objects , And return a tuple list . Each tuple groups the elements of the input object according to the location index .

You can also call objects to “ decompression ” object *zip().

At the end

Python It is a very diverse and well developed language , So there will certainly be many functions I haven't considered . If you want to know more about python modular , You can refer to awesome-python.

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