学习笔记－第二章

安装ipython

pip install python

进入python交互环境

$ ipython
Python 2.7.10 (default, Oct 23 2015, 19:19:21) 
Type "copyright", "credits" or "license" for more information.

IPython 5.1.0 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.

In [1]：

内置json模块可讲json字符串转换为python字典对象

• json.loads(json_str) #导入json字符串，生成字典对象

collections.Counter类

• collections.Counter(list_value) 能获取list列表里各元素的个数，并生成一个counter对象
  In [58]: counts = Counter(time_zones)

  In [59]:  type(counts)
   Out[59]: collections.Counter
  
  In [60]: 
  

• most_common(number)方法能获取前number个元素的个数
  In [60]: counts.most_common(10)
  Out[60]:
  [(u'America/New_York', 1251),
  (u'', 521),
  (u'America/Chicago', 400),
  (u'America/Los_Angeles', 382),
  (u'America/Denver', 191),
  (u'Europe/London', 74),
  (u'Asia/Tokyo', 37),
  (u'Pacific/Honolulu', 36),
  (u'Europe/Madrid', 35),
  (u'America/Sao_Paulo', 33)]
  In [61]:

用pandas对元素进行计数

• DAtaFrame是pandas中重要的数据结构，将数据表示为一个表格y