Python学习笔记2-解析数据

Import os; -- Python自带

print(os.getcwd()) -- 获得当前工作目录

os.chdir('/Users/longlong/Documents') -- 转换到/Users/longlong/Documents目录

os.path.join(parm1, parm2,...) -- 从一个或多个路径片段中构造一个路径名。

os.path.expanduser() -- 用来将包含~符号的路径扩展为完整的路径

 

>>> pathname = '/Users/pilgrim/diveintopython3/examples/humansize.py'
>>> os.path.split(pathname)  --('/Users/pilgrim/diveintopython3/examples', 'humansize.py')罗列目录内容构造绝对路径

 

>>> import os

>>> print(os.getcwd())

/Users/longlong/Documents

>>> os.chdir("./python/")

>>> os.getcwd()

'/Users/longlong/Documents/python'

>>> print(os.path.realpath('whileloop.py')

      )

/Users/longlong/Documents/python/whileloop.py

>>> print(os.path.realpath("whileloop.py"))

/Users/longlong/Documents/python/whileloop.py

>>> 

 

 

列表解析

>>> [os.path.realpath(f) for f in glob.glob("*.py")]

['/Users/longlong/Documents/python/indices_over_two_objects.py', '/Users/longlong/Documents/python/loops_over_indices.py', '/Users/longlong/Documents/python/while_loops.py']
>>> [f for f in glob.glob("*.py") if os.stat(f).st_size > 700] ['indices_over_two_objects.py', 'while_loops.py']
 
  

 

字典解析

>>> metadat_dict = { f:os.stat(f) for f in glob.glob('*.py')}



>>> type(metadat_dict)

<class 'dict'>



>>> list(metadat_dict.keys())

['indices_over_two_objects.py', 'while_loops.py', 'loops_over_indices.py']



>>> metadat_dict['indices_over_two_objects.py'].st_size

871

 

>>> list(metadat_dict.keys())

['indices_over_two_objects.py', 'while_loops.py', 'loops_over_indices.py']



>>> a_dict = {'a':1, 'b':2,'c':3}

>>> {value:key for key,value in a_dict.items()}

{1: 'a', 2: 'b', 3: 'c'}

 

集合解析

>>> a_set = set(range(10))

>>> a_set

{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}



>>> {x**2 for x in a_set}

{0, 1, 64, 4, 36, 9, 16, 49, 81, 25}



>>> {x for x in a_set if x%2 == 0 }

{0, 8, 2, 4, 6}



>>> {2**x for x in range(10)}

{32, 1, 2, 64, 4, 128, 256, 512, 8, 16}

 

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