七、 Python第三方包

1 优化代码异常输出包

一行代码优化输出的异常信息

pip install pretty-errors

写一个函数测试：

def divided_zero():
    for i in range(10, -1, -1):
        print(10/i)


divided_zero()

在没有import这个pretty-errors前，输出的错误信息有些冗余：

Traceback (most recent call last):
  File "c:\Users\HUAWEI\.vscode\extensions\ms-python.python-2019.11.50794\pythonFiles\ptvsd_launcher.py", line 43, in <module>
    main(ptvsdArgs)
  File "c:\Users\HUAWEI\.vscode\extensions\ms-python.python-2019.11.50794\pythonFiles\lib\python\old_ptvsd\ptvsd\__main__.py",
line 432, in main
    run()
  File "c:\Users\HUAWEI\.vscode\extensions\ms-python.python-2019.11.50794\pythonFiles\lib\python\old_ptvsd\ptvsd\__main__.py",
line 316, in run_file
    runpy.run_path(target, run_name='__main__')
  File "D:\anaconda3\lib\runpy.py", line 263, in run_path
    pkg_name=pkg_name, script_name=fname)
  File "D:\anaconda3\lib\runpy.py", line 96, in _run_module_code
    mod_name, mod_spec, pkg_name, script_name)
  File "D:\anaconda3\lib\runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "d:\source\sorting-visualizer-master\sorting\debug_test.py", line 6, in <module>
    divided_zero()
  File "d:\source\sorting-visualizer-master\sorting\debug_test.py", line 3, in divided_zero
    print(10/i)
ZeroDivisionError: division by zero

我们使用刚安装的pretty_errors，import下:

import pretty_errors

def divided_zero():
    for i in range(10, -1, -1):
        print(10/i)

divided_zero()

此时看看输出的错误信息，非常精简只有2行，去那些冗余信息：

ZeroDivisionError:
division by zero

完整的输出信息如下图片所示：

2 图像处理包pillow

两行代码实现旋转和缩放图像

首先安装pillow:

pip install pillow

旋转图像下面图像45度：

In [1]: from PIL import Image
In [2]: im = Image.open('./img/plotly2.png')
In [4]: im.rotate(45).show()

旋转45度后的效果图

等比例缩放图像：

im.thumbnail((128,72),Image.ANTIALIAS)

缩放后的效果图：

过滤图像后的效果图：

from PIL import ImageFilter
im.filter(ImageFilter.CONTOUR).show()