python基础学习笔记

数字自加操作

>>> n=1
>>> n=n+1
>>> print n
2
>>> n += 1
>>> print n
3

格式化输出数字

>>> print 'float n:%f
init  n:%d' % (n,n)
float n:3.000000
init  n:3
>>> print '%0.3f' % n
3.000
>>> print '%0.4f' % n
3.0000
>>>

字符串切片操作

>>> s = 'football'
>>> s[0]
'f'
>>> s[0:]
'football'
>>> s[1:]
'ootball'
>>> s[1:2]
'o'
>>> s[:3]
'foo'
>>> s[1:1]
''
>>> s[1:-1]
'ootball'
>>> s[1:0]
''

字符串加法和乘法

>>> s *2
'footballfootball'
>>> s += 'a'
>>> s
'footballa'
>>> print '-'*20
--------------------
>>> print '-'*40
----------------------------------------

列表切片与元素赋值操作

>>> alist = ['a','b','c','d','e']
>>> print alist
['a', 'b', 'c', 'd', 'e']
>>> alist[0]
'a'
>>> alist[1:-1]
['b', 'c', 'd']
>>> alist[1:3]
['b', 'c']
>>> alist[:3]
['a', 'b', 'c']
>>> alist[0]='f'
>>> alist
['f', 'b', 'c', 'd', 'e']
>>>

元组切片操作

注：元组中的元素不能重新赋值

>>> 
>>> aTuple = (1,2,3,4,5,6)
>>> aTuple
(1, 2, 3, 4, 5, 6)
>>> aTuple[:3]
(1, 2, 3)
>>> aTuple[5]=4
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'tuple' object does not support item assignment

字典赋值、读取、更新和key操作

>>> hostdict={'name':'server01','ip':'192.168.10.10','port':'8080'}
>>> hostdict
{'ip': '192.168.10.10', 'name': 'server01', 'port': '8080'}
>>> hostdict['name']
'server01'
>>> hostdict['ip']='192.168.10.11'
>>> hostdict
{'ip': '192.168.10.11', 'name': 'server01', 'port': '8080'}
>>> hostdict.keys()
['ip', 'name', 'port']
>>> for key in hostdict:
...     print '%s	%s' % (key,hostdict[key])
... 
ip        192.168.10.11
name      server01
port      8080
>>>

列表解析

>>> a=[x + 2 for x in range(5)]
>>> a
[2, 3, 4, 5, 6]
>>> b=[x * 2 for x in s]
>>> b
['ff', 'oo', 'oo', 'tt', 'bb', 'aa', 'll', 'll']
>>> c =[x ** 2 for x in range(8) if x % 2]
>>> c
[1, 9, 25, 49]
>>>

dir操作获取模块的方法和属性

>>> import sys
>>> dir(sys)
['__displayhook__', '__doc__', '__egginsert', '__excepthook__', '__name__', '__package__', '__plen', '__stderr__', '__stdin__', '__stdout__', '_clear_type_cache', '_current_frames', '_getframe', 'api_version', 'argv', 'builtin_module_names', 'byteorder', 'call_tracing', 'callstats', 'copyright', 'displayhook', 'dont_write_bytecode', 'exc_clear', 'exc_info', 'exc_type', 'excepthook', 'exec_prefix', 'executable', 'exit', 'flags', 'float_info', 'getcheckinterval', 'getdefaultencoding', 'getdlopenflags', 'getfilesystemencoding', 'getprofile', 'getrecursionlimit', 'getrefcount', 'getsizeof', 'gettrace', 'hexversion', 'last_traceback', 'last_type', 'last_value', 'maxint', 'maxsize', 'maxunicode', 'meta_path', 'modules', 'path', 'path_hooks', 'path_importer_cache', 'platform', 'prefix', 'ps1', 'ps2', 'py3kwarning', 'setcheckinterval', 'setdlopenflags', 'setprofile', 'setrecursionlimit', 'settrace', 'stderr', 'stdin', 'stdout', 'subversion', 'version', 'version_info', 'warnoptions']
>>> print sys.getfilesystemencoding
<built-in function getfilesystemencoding>
>>> print sys.getfilesystemencoding()
UTF-8
>>>