XML 数据

xml_data = '''<?xml version="1.0" encoding="UTF-8"?>
<books>
    <book SN="12460901">
        <name>国富论</name>
        <author nation="English">亚当·斯密</author>
        <price>108</price>
        <ISBN>9787511373229</ISBN>
    </book>
    <book SN="12257413">
        <name>原则</name>
        <author nation="America">瑞·达利欧</author>
        <price>98</price>
        <ISBN>9787508684031</ISBN>
    </book>
</books>
'''

xml.etree.ElementTree 导入 import xml.

安装

Python

sudo apt install python3
sudo apt install python3-pip
sudo pip3 install --upgrade pip

OpenCV

sudo pip3 install opencv-python
sudo pip3 install opencv-contrib-python

图像

读取图像

import cv2

img_file = 'python-logo@2x.png'
img = cv2.imread(img_file)

获取图像大小

width = img.shape[1]
height = img.shape[0]

显示图像并等待按任意键退出

import cv2

img_file = 'python-logo@2x.png'
img = cv2.imread(img_file)
cv2.imshow('', img)
cv2.waitKey(0)

宽高缩小一倍 比例 import cv2 img_file = 'python-logo@2x.png' img = cv2.imread(img_file) img = cv2.resize(img, None, fx=0.5, fy=0.5) cv2.

file.write() 内容超过 4K 才会写入磁盘

验证代码

import os
import tempfile

for count in range(1, 4100):
    content = '0'*count
    with tempfile.NamedTemporaryFile() as file:
        print(file.name)
        file.write(content.encode())

        with open(file.name, 'r') as tf:
            content_len = len(tf.read())
            if content_len > 0:
                print(f'{count} bytes written successfully.')

运行结果 /var/folders/bc/7lz308t90gb1h1xw6k4j65x80000gn/T/tmpj458ozas /var/folders/bc/7lz308t90gb1h1xw6k4j65x80000gn/T/tmpmrxo8sg1 /var/folders/bc/7lz308t90gb1h1xw6k4j65x80000gn/T/tmp0hu_i4hz 4097 bytes written successfully.