python标准库学习3
import operatorsequence = 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 = [, , ]
b = copy.copy( a )
print "before", "=>"
print a
print b
# modify original
a = 0
a = None
print "after", "=>"
print a
print b
输出的结果是：
before =>
[, , ]
[, , ]
after =>
[, None, ]
[, , ]
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 ) == ".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 = item
list = AutoList()
for i in range( 10 ):
list = i
print list
输出的结果为：
随机数：
import random
for i in range(5):
# random float: 0.0
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