Python Code Snippets

李家翔

2020-01-31

1. 使用 RMarkdown 的 child 参数，进行文档拼接。
2. 这样拼接以后的笔记方便复习。
3. 相关问题提交到 Issue

参考 Grifski (2019)

1 build dict

column_names = ['id', 'color', 'style']
column_values = [1, 'red', 'bold']

sample_dict = dict(zip(column_names, column_values))

sample_dict

{'id': 1, 'color': 'red', 'style': 'bold'}

{key:value for key, value in zip(column_names, column_values)}

{'id': 1, 'color': 'red', 'style': 'bold'}

启发下面。

2 flip keys and values when values is distinct

{value: key for key, value in sample_dict.items()}

{1: 'id', 'red': 'color', 'bold': 'style'}

dict(map(reversed, sample_dict.items()))

{1: 'id', 'red': 'color', 'bold': 'style'}

3 merge each value of two lists

ethernet_devices = [1, [7], [2], [8374163], [84302738]]
usb_devices = [1, [7], [1], [2314567], [0]]

# list comprehension
[x + y for x, y in zip(ethernet_devices, usb_devices)]

[2, [7, 7], [2, 1], [8374163, 2314567], [84302738, 0]]

import numpy as np

np.add(ethernet_devices, usb_devices)

array([2, list([7, 7]), list([2, 1]), list([8374163, 2314567]),
       list([84302738, 0])], dtype=object)

如果是 int 结构就直接相加，如果是 list 结构就合并。

4 Check if a file exist

import os

os.path.isfile("some/path")

False

5 Check if a List is empty

sample_list = list()

if not sample_list:
    pass

6 Get the last one of a list

my_list = ['red', 'blue', 'green']

my_list[-1]

'green'

7 sort dict

csv_mapping_list = [
  {
    "Name": "Jeremy",
    "Age": 25,
    "Favorite Color": "Blue"
  },
  {
     "Name": "Ally",
     "Age": 41,
     "Favorite Color": "Magenta"
  },
  {
    "Name": "Jasmine",
    "Age": 29,
    "Favorite Color": "Aqua"
  }
]

csv_mapping_list.sort(key=lambda item: item.get("Age"))

csv_mapping_list

[{'Name': 'Jeremy', 'Age': 25, 'Favorite Color': 'Blue'},
 {'Name': 'Jasmine', 'Age': 29, 'Favorite Color': 'Aqua'},
 {'Name': 'Ally', 'Age': 41, 'Favorite Color': 'Magenta'}]

8 merge two dict

yusuke_power = {"Yusuke Urameshi": "Spirit Gun"}
hiei_power = {"Hiei": "Jagan Eye"}
powers = dict()

powers = yusuke_power.copy()

powers.update(hiei_power)

powers

{'Yusuke Urameshi': 'Spirit Gun', 'Hiei': 'Jagan Eye'}

{**yusuke_power, **hiei_power}

{'Yusuke Urameshi': 'Spirit Gun', 'Hiei': 'Jagan Eye'}

9 print string like glue

name = 'Jeremy'
age = 25

print("My name is " + name + ", and I am " + str(age) + " years old.")

My name is Jeremy, and I am 25 years old.

# String formatting using f-Strings (Python 3.6+)
print('My name is {name}, and I am {age} years old.')

My name is {name}, and I am {age} years old.

# String formatting using modulus operator
print('My name is %s, and I am %d years old.' % (name, age))

My name is Jeremy, and I am 25 years old.

# String formatting using format function with ordered parameters
print('My name is {}, and I am {} years old.'.format(name, age))
# String formatting using format function with named parameters
print('My name is {a}, and I am {b} years old.'.format(a=name, b=age))

My name is Jeremy, and I am 25 years old.
My name is Jeremy, and I am 25 years old.

10 avoid newline

print("Hello,", end='')
print("Hello")

Hello,Hello

附录

参考文献

Grifski, Jeremy. 2019. “71 Python Code Snippets for Everyday Problems.” The Renegade Coder. 2019. https://therenegadecoder.com/code/python-code-snippets-for-everyday-problems/.