打印 Python 的一切 —— pprint & beeprint

打印，是所有程序员从小白时期就具备的神技，遇事不决打印一下，是 DEBUG 最简单且不依赖 IDE 的方式，自定义各种日志输出，也是项目成型后必备功能。
但是为了优雅的打印格式，往往需要对各种对象进行特殊格式化，可遇到字典和大段字符串也不好处理。
这篇文章介绍两个库模块，可以快速有效的解决所有 Python 对象的打印输出，没错，所有。

pprint

这是 Python 标准库模块，全称 pretty printer，可以让各种数据结构更美观地输出。

>>> print(game)

{'players': [{'name': 'player_1', 'hp': 3}, {'name': 'player_2', 'hp': 5}]}

>>> pprint.pprint(game, width=4)

{'players': [{'hp': 3,

              'name': 'player_1'},

             {'hp': 5,

              'name': 'player_2'}]}

pprint.pprint(object, stream=None, indent=1, width=80, depth=None, *, compact=False)

stream：输出流，默认是 sys.stdout ，也就是屏幕输出。
indent：缩进空格数。
width：每行最大宽度，默认为80个字符，超过宽度会换行，但如果单个对象超过不会被换行，比如一段长字符串。
depth：限制数据的层级，设置后可以限制过多的嵌套。
compact：3.4版本新加入的参数，若设为 True ，则输出会在接近 width 限制才进行换行。

>>> pprint.pprint(stuff, indent=4)

[   ['spam', 'eggs', 'lumberjack', 'knights', 'ni'],

    'spam',

    'eggs',

    'lumberjack',

    'knights',

    'ni']

>>> pprint.pprint(stuff, width=41, compact=True)

[['spam', 'eggs', 'lumberjack',

  'knights', 'ni'],

 'spam', 'eggs', 'lumberjack', 'knights',

 'ni']

pprint.pformat(object, indent=1, width=80, depth=None, *, compact=False)

和 pprint.pprint 的区别是，该函数不会打印到输出流，而是返回一个格式化字符串。

>>> stuff = ['spam', 'eggs', 'lumberjack', 'knights', 'ni']

>>> stuff.insert(0, stuff)

>>> pprint.pprint(stuff)

[<Recursion on list with id=...>,

 'spam',

 'eggs',

 'lumberjack',

 'knights',

 'ni']

classpprint.PrettyPrinter(indent=1, width=80, depth=None, stream=None, *, compact=False)

上文两个函数，实际都是构建一个 PrettyPrinter 对象，并调用对应的方法，所以当需要复用格式化的时候，我们可以提前构建该对象。

>>> pp = pprint.PrettyPrinter(width=40, compact=True)

>>> pp.pprint(game)

{'players': [{'hp': 3,

              'name': 'player_1'},

             {'hp': 5,

              'name': 'player_2'}]}

>>> pp.pprint(stuff)

['spam', 'eggs', 'lumberjack',

 'knights', 'ni']

pprint 对字典列表这类数据结构确实很好用，但遇到类、字符串仍然和 print 差别不大，因此这里有一个国人写的第三方库介绍给大家。

beeprint

除了和 pprint 一样支持 dict, list, tuple 等常规变量的格式化输出，还支持 object 变量打印、长文本自动剪切。

下面是作者 README 中和 pprint 的对比：

pprint:

{'entities': {'hashtags': [],

              'urls': [{'display_url': 'tumblr.com/xnr37hf0yz',

                        'expanded_url': 'http://tumblr.com/xnr37hf0yz',

                        'indices': [107, 126],

                        'url': 'http://t.co/cCIWIwg'}],

              'user_mentions': []}}

beeprint:

{

  'entities': {

    'hashtags': [],

    'urls': [

      {

        'display_url': 'tumblr.com/xnr37hf0yz',

        'expanded_url': 'http://tumblr.com/xnr37hf0yz',

        'indices': [107, 126],

        'url': 'http://t.co/cCIWIwg',

      },

    ],

    'user_mentions': [],

  },

}

pprint:

<class 'definition.NormalClassNewStyle'>

beeprint:

class(NormalClassNewStyle):

  dicts: {

  },

  lists: [],

  static_props: 1,

  tuple: (1, 2)

pprint:

<definition.NormalClassNewStyle object at 0x7f338e5a9dd0>

beeprint:

instance(NormalClassNewStyle):

  dicts: {

  },

  lists: [],

  say_hi: 'hello world',

  static_props: 1,

  tuple: (1, 2)

pprint:

[['\nThe sky and the earth were at first one blurred entity like an egg. Pangu was born into it.\n \n\tThe separation of the sky and the earth took eighteen thousand years-the yang which was light and pure rose to become the sky, \tand the yin which was heavy and murky\xef\xbc\x88\xe6\x9c\xa6\xe8\x83\xa7\xe7\x9a\x84\xef\xbc\x89 sank to form the earth. Between them was Pangu, who went through nine \tchanges every day, his wisdom greater than that of the sky and his ability greater than that of the earth. Every day the sky rose ten feet higher, the earth became ten feet thicker, and Pangu grew ten feet taller.\n \nAnother eighteen thousand years passed, and there was an extremely high sky, an extremely thick earth, and an extremely tall Pangu. After Pangu died, his head turned into the Five Sacred Mountains (Mount Tai, Mount Heng, Mount Hua, Mount Heng, Mount Song), his eyes turned into the moon and the sun, his blood changed into water in river and sea, his hair into grass.\n \nIn all, the universe and Pangu combine in one.\n',

  '\n\xe6\x8d\xae\xe6\xb0\x91\xe9\x97\xb4\xe7\xa5\x9e\xe8\xaf\x9d\xe4\xbc\xa0\xe8\xaf\xb4\xe5\x8f\xa4\xe6\x97\xb6\xe7\x9b\x98\xe5\x8f\xa4\xe7\x94\x9f\xe5\x9c\xa8\xe9\xbb\x91\xe6\x9a\x97\xe5\x9b\xa2\xe4\xb8\xad\xef\xbc\x8c\xe4\xbb\x96\xe4\xb8\x8d\xe8\x83\xbd\xe5\xbf\x8d\xe5\x8f\x97\xe9\xbb\x91\xe6\x9a\x97\xef\xbc\x8c\xe7\x94\xa8\xe7\xa5\x9e\xe6\x96\xa7\xe5\x8a\x88\xe5\x90\x91\xe5\x9b\x9b\xe6\x96\xb9\xef\xbc\x8c\xe9\x80\x90\xe6\xb8\x90\xe4\xbd\xbf\xe5\xa4\xa9\xe7\xa9\xba\xe9\xab\x98\xe8\xbf\x9c\xef\xbc\x8c\xe5\xa4\xa7\xe5\x9c\xb0\xe8\xbe\xbd\xe9\x98\x94\xe3\x80\x82\n\t\xe4\xbb\x96\xe4\xb8\xba\xe4\xb8\x8d\xe4\xbd\xbf\xe5\xa4\xa9\xe5\x9c\xb0\xe4\xbc\x9a\xe9\x87\x8d\xe6\x96\xb0\xe5\x90\x88\xe5\xb9\xb6\xef\xbc\x8c\xe7\xbb\xa7\xe7\xbb\xad\xe6\x96\xbd\xe5\xb1\x95\xe6\xb3\x95\xe6\x9c\xaf\xe3\x80\x82\xe6\xaf\x8f\xe5\xbd\x93\xe7\x9b\x98\xe5\x8f\xa4\xe7\x9a\x84\xe8\xba\xab\xe4\xbd\x93\xe9\x95\xbf\xe9\xab\x98\xe4\xb8\x80\xe5\xb0\xba\xef\xbc\x8c\xe5\xa4\xa9\xe7\xa9\xba\xe5\xb0\xb1\xe9\x9a\x8f\xe4\xb9\x8b\xe5\xa2\x9e\xe9\xab\x98\xe4\xb8\x80\xe5\xb0\xba\xef\xbc\x8c\n\t\xe7\xbb\x8f\xe8\xbf\x871.8\xe4\xb8\x87\xe5\xa4\x9a\xe5\xb9\xb4\xe7\x9a\x84\xe5\x8a\xaa\xe5\x8a\x9b\xef\xbc\x8c\xe7\x9b\x98\xe5\x8f\xa4\xe5\x8f\x98\xe6\x88\x90\xe4\xb8\x80\xe4\xbd\x8d\xe9\xa1\xb6\xe5\xa4\xa9\xe7\xab\x8b\xe5\x9c\xb0\xe7\x9a\x84\xe5\xb7\xa8\xe4\xba\xba\xef\xbc\x8c\xe8\x80\x8c\xe5\xa4\xa9\xe7\xa9\xba\xe4\xb9\x9f\xe5\x8d\x87\xe5\xbe\x97\xe9\xab\x98\xe4\xb8\x8d\xe5\x8f\xaf\xe5\x8f\x8a\xef\xbc\x8c\xe5\xa4\xa7\xe5\x9c\xb0\xe4\xb9\x9f\xe5\x8f\x98\xe5\xbe\x97\xe5\x8e\x9a\xe5\xae\x9e\xe6\x97\xa0\xe6\xaf\x94\xe3\x80\x82\xe7\x9b\x98\xe5\x8f\xa4\xe7\x94\x9f\xe5\x89\x8d\xe5\xae\x8c\xe6\x88\x90\xe5\xbc\x80\xe5\xa4\xa9\xe8\xbe\x9f\xe5\x9c\xb0\xe7\x9a\x84\xe4\xbc\x9f\xe5\xa4\xa7\xe4\xb8\x9a\xe7\xbb\xa9\xef\xbc\x8c\xe6\xad\xbb\xe5\x90\x8e\xe6\xb0\xb8\xe8\xbf\x9c\xe7\x95\x99\xe7\xbb\x99\xe5\x90\x8e\xe4\xba\xba\xe6\x97\xa0\xe7\xa9\xb7\xe6\x97\xa0\xe5\xb0\xbd\xe7\x9a\x84\xe5\xae\x9d\xe8\x97\x8f\xef\xbc\x8c\xe6\x88\x90\xe4\xb8\xba\xe4\xb8\xad\xe5\x8d\x8e\xe6\xb0\x91\xe6\x97\x8f\xe5\xb4\x87\xe6\x8b\x9c\xe7\x9a\x84\xe8\x8b\xb1\xe9\x9b\x84\xe3\x80\x82\n']]

beeprint:

[

  [

    '\nThe sky and the earth were at first one blurred entity like an egg. Pangu

     was born into it.\n \n\tThe separation of the sky and the earth took

     ...(12 hidden lines)',

    '\n据民间神话传说古时盘古生在黑暗团中，他不能忍受黑暗，用神斧劈向四方，逐渐

     使天空高远，大地辽阔。\n\t他为不使天地会重新合并，继续施展法术。每当盘古的

     ...(3 hidden lines)',

  ],

]

beeprint.pp(o, output=True, max_depth=5, indent=2, width=80, sort_keys=True, config=None, **kwargs):

参数和 pprint 类似，多出了 sort_keys可以打印字典时是否按 key 排序（ pprint 是默认排序，不可选），另外还有控制文本裁剪等行为的参数，可以从 beeprint.Config 里查看。

该库的 Github：https://github.com/panyanyany/beeprint

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