python标准库学习3

import operator

sequence = 1, 2, 4

print "add", "=>", reduce(operator.add, sequence)
print "sub", "=>", reduce(operator.sub, sequence)
print "mul", "=>", reduce(operator.mul, sequence)
print "concat", "=>", operator.concat("spam", "egg")
print "repeat", "=>", operator.repeat("spam", 5)
print "getitem", "=>", operator.getitem(sequence, 2)
print "indexOf", "=>", operator.indexOf(sequence, 2)
print "sequenceIncludes", "=>", operator.sequenceIncludes(sequence, 3)

add => 7

sub => -5

mul => 8

concat => spamegg

repeat => spamspamspamspamspam

getitem => 4

indexOf => 1

sequenceIncludes => False

注意copy中的一些问题：

import copy

a = [[1], [2], [3]]
b = copy.copy( a )

print "before", "=>"
print a
print b

# modify original
a[0][0] = 0
a[1] = None

print "after", "=>"
print a
print b

输出的结果是：

before =>

[[1], [2], [3]]

[[1], [2], [3]]

after =>

[[0], None, [3]]

[[0], [2], [3]]

测量算法的运行时间：

import time

def procedure():
    time.sleep( 2.5 )

# measure process time
t0 = time.clock()
procedure()
print time.clock() - t0, "seconds process time"

# measure wall time
t0 = time.time()
procedure()
print time.time() - t0, "seconds wall time"

循环读文本文件：

import fileinput
import sys

for line in fileinput.input( "../src/hello.xml" ):
    sys.stdout.write( "-> " )
    sys.stdout.write( line )

import fileinput
import glob
import string, sys

for line in fileinput.input( glob.glob( "../src/hello.xml" ) ):
    if fileinput.isfirstline(): # first in a file?
        sys.stderr.write( "-- reading %s --\n" % fileinput.filename() )
    sys.stdout.write( str( fileinput.lineno() ) + " " + string.upper( line ) )

复制文件的操作：

import os , shutil
print os.listdir( "../src" )

for file in os.listdir( "../src" ):
    if os.path.splitext( file )[1] == ".py":
        os.mkdir( "../src/back" )
        print file
        shutil.copy( file, os.path.join( "back", file ) )
        
    

可以使用shutil开复制整个目录,然后删除目录

import os , shutil
print os.listdir( ".." )
shutil.copytree("../src", "../src1")
shutil.rmtree( "../src1" )

想内存文件写入内容：

import StringIO

file = StringIO.StringIO()
file.write( "This man is no ordinary man. " )
file.write( "This is Mr. F. G. Superman." )

print file.getvalue()

使用StringIO模块捕获输出：

import StringIO
import string, sys

stdout = sys.stdout

sys.stdout = file = StringIO.StringIO()

print """a"""

sys.stdout = stdout

print string.upper( file.getvalue() )

结果输出A

也可以使用cStringIO：

import cStringIO
file = cStringIO.StringIO( "asdaskdgaksdgkasdja" )
print file.getvalue()
print file.read()

小技巧：由于cStringIO比StringIO的效率高一点，但是兼容性不行，所以可以使用下面的语句：

try:
    import cStringIO
    StringIO = cStringIO
except ImportError:
    import StringIO

print StringIO

类继承的时候构造函数的一点点问题：

class A:
    def __init__( self ):
        pass
class B( A ):
    def __init__( self ):
        #A.__init__( self )
        super( B, self ).__init__( self )
    

对字典使用“+”法

import UserDict

class Add( UserDict.UserDict ):
    def __init__( self, dict = {}, **kwargs ):
        UserDict.UserDict.__init__( self )
        self.update( dict )
        self.update( kwargs )
    def __add__( self, other ):
        dict = Add( self.data )
        dict.update( other )
        return dict

a = Add( a = 1 )
b = Add( b = 2 )
print a + b

输出的结果为:{'a': 1, 'b': 2}

实例类似一个普通的列表对象, 但它允许你通过赋值为列表添加项目.

import UserList

class AutoList( UserList.UserList ):
    def __init__( self ):
        super( AutoList, self ).__init__( self )
    def __setitem__( self, i, item ):
        if i == len( self.data ):
            self.append( item )
        else:
            self.data[i] = item

list = AutoList()

for i in range( 10 ):
    list[i] = i
print list        

输出的结果为：[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

随机数：

import random

for i in range(5):

    # random float: 0.0 <= number < 1.0
    print random.random(),

    # random float: 10 <= number < 20
    print random.uniform(10, 20),

    # random integer: 100 <= number <= 1000
    print random.randint(100, 1000),

    # random integer: even numbers in 100 <= number < 1000
    print random.randrange(100, 1000, 2)

随机打乱序列的顺序：

import random

a = range( 10 )
print a
random.shuffle( a )
print a

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

[5, 2, 6, 9, 4, 7, 3, 8, 0, 1]

你的结果可能不一样