python之pprint模块

学过perl同学都知道perl有Data::Dumper,在python有相同功能模块pprint。接下来会把学习python文档做些笔记，以便以后查阅。pprint能够打印python的数据结构，看起来更直观。

PrettyPrinter类有三个参数：indent, depth, width

indent:展示数据时，缩进多少(每个递归层)
depth:最多显示层级
width:展示一行宽度，默认80

对每层递归都缩进10

>>> import pprint>>> stuff = ['a'*10, 'b'*10, 'c'*10, 'd'*10, 'e'*10]>>> stuff.insert(0, stuff[:])>>> pp = pprint.PrettyPrinter(indent=10);>>> pp.pprint(stuff)[         [         'aaaaaaaaaa',                    'bbbbbbbbbb',                    'cccccccccc',                    'dddddddddd',                    'eeeeeeeeee'],          'aaaaaaaaaa',          'bbbbbbbbbb',          'cccccccccc',          'dddddddddd',          'eeeeeeeeee']

一共是6层，如果只显示5层，那python就会用”…”来展示为未显示列表

>>> tup = ('a', ('b', ('c', ('d', ('e', ('f',))))))>>> pp = pprint.PrettyPrinter(depth=6)>>> pp.pprint(tup)('a', ('b', ('c', ('d', ('e', ('f',))))))>>> pp = pprint.PrettyPrinter(depth=5)>>> pp.pprint(tup)('a', ('b', ('c', ('d', ('e', (...,))))))

一共是92个字符，所以width=93时，就可在一行内放下

>>> stuff = ['a'*5, 'b'*5, 'c'*5, 'd'*5, 'e'*5]>>> stuff.insert(0, stuff[:])>>> pp = pprint.PrettyPrinter();>>> pp.pprint(stuff)[['aaaaa', 'bbbbb', 'ccccc', 'ddddd', 'eeeee'], 'aaaaa', 'bbbbb', 'ccccc', 'ddddd', 'eeeee']>>> pp = pprint.PrettyPrinter(width=93);>>> pp.pprint(stuff);[['aaaaa', 'bbbbb', 'ccccc', 'ddddd', 'eeeee'], 'aaaaa', 'bbbbb', 'ccccc', 'ddddd', 'eeeee']

PrettyPrinter的函数:pformat、pprint、isreadable、isrecursive、saferepr
具体参考(http://docs.python.org/library/pprint.html)

pformat以字符串返回

>>> stuff = ['a'*5, 'b'*5, 'c'*5, 'd'*5, 'e'*5]>>> pp = pprint.PrettyPrinter();>>> pp.pformat(stuff);"['aaaaa', 'bbbbb', 'ccccc', 'ddddd', 'eeeee']"

Print the formatted representation of object on the configured stream(不知道怎么翻译好)

>>> stuff = ['a'*5, 'b'*5, 'c'*5, 'd'*5, 'e'*5]>>> stuff.insert(0, stuff)>>> pprint.pprint(stuff)[<Recursion on list with id=29923736>, 'aaaaa', 'bbbbb', 'ccccc', 'ddddd', 'eeeee']

isreadable来确认对象是否可读，如果是递归对象(多层)，就会返回false

>>> stuff = ['a'*5, 'b'*5, 'c'*5, 'd'*5, 'e'*5]>>> pp = pprint.PrettyPrinter();>>> pp.isreadable(stuff)True>>> stuff.insert(0, stuff)   >>> pp.isreadable(stuff)False

isrecursive判断是否是递归对象

>>> stuff = ['a'*5, 'b'*5, 'c'*5, 'd'*5, 'e'*5] >>> pp = pprint.PrettyPrinter();>>> pp.isrecursive(stuff)False>>> stuff.insert(0, stuff)>>> pp.isrecursive(stuff)True

对递归对象进行保护，递归对象就会显示

>>> pprint.saferepr(stuff)"[<Recursion on list with id=29924312>, 'aaaaa', 'bbbbb', 'ccccc', 'ddddd', 'eeeee']"