python学习笔记—— 函数
〈p>读取远程页面
from urllib import urlretrieve
def printFile(url):
f = open(url)
for line in f:
if line.strip():
print line
f.close()
def loadFile(url=r'http://www.idkin.com/contact.html', process=printFile):
try:
fileName = urlretrieve(url,'tmp.html')[0]
print(fileName)
except BaseException, e:
print(str(e))
if fileName:
process(fileName)
if __name__ == "__main__":
loadFile()
#urlretrieve的返回值是一个tuple， 第一个元素就是目标文件名
#如果urlretrieve仅获取一个参数，返回值的第一个元素就是产生的临时文件名
filter函数,类似javascript1.7的Array#filter。filter函数的功能相当于过滤器。调用一个布尔函数fn来迭代遍历每个seq中的元素；返回一个使fn返回值为true的元素的序列。
from random import randint
def filter(fn,arr):
ret = [];
for i in arr:
if fn(i):
ret.append(i)
return ret;
arr = [1,2,3,4,5,6];
print filter(lambda n:n%2,arr)
map函数,类似javascript1.7的Array#map。map函数func作用于给定序列的每个元素，并用一个列表来提供返回值。
from random import randint
def map(fn,arr):
ret = [];
for i in arr:
ret.append(fn(i))
return ret;
arr = [1,2,3,4,5,6];
print map(lambda n:n+10,arr)
我们也可以用并归的思想实现此迭代器:
def rmap ( fun, list ):
if list == []:
return []
else:
return [fun( list[0] )] + rmap( fun, list[1:] )
reduce函数,类似javascript1.7的Array#reduce。fn为二元函数，将fn作用于seq序列的元素，每次携带一对（先前的结果以及下一个序列的元素），连续的将现有的结果和下一个值作用在获得的随后的结果上，最后减少我们的序列为一个单一的返回值。
from random import randint
def reduce(fn,seq,initial=None):
lseq = list(seq)
if initial is None:
res = lseq.pop(0)
else:
res = initial
for i in lseq:
res = fn(res,i)
return res
arr = [1,2,3,4,5,6];
print reduce(lambda a,b:a+b,arr)
追踪闭包词法的变量
output = 'int %r id=%#0x val=%d'
w = x = y =z =1
def f1():
x = y = z = 2
def f2():
y = z = 3
def f3():
z = 4
print output %('w', id(w),w)
print output %('x', id(x),x)
print output %('y', id(y),y)
print output %('z', id(z),z)
clo = f3.func_closure
if clo:
print "f3 closure vars: ",[str(c) for c in clo]
else:
print "no f3 closure vars"
f3()
clo = f2.func_closure
if clo:
print "f2 closure vars: ",[str(c) for c in clo]
else:
print "no f2 closure vars"
f2()
clo = f1.func_closure
if clo:
print "f1 closure vars: ",[str(c) for c in clo]
else:
print "no f1 closure vars"
f1()
打印日志
# coding='utf-8'
from time import time
def logged(when):
def log(f,*args,**kargs):
print '''Called:
function:%s
args:%r
kargs:%r''' % (f,args,kargs)
def pre_logged(f):
def wrapper(*args,**kargs):
log(f,*args,**kargs)
return f(*args,**kargs)
return wrapper
def post_logged(f):
def wrapper(*args,**kargs):
now=time()
try:
return f(*args,**kargs)
finally:
log(f,*args,**kargs)
print "time delta: %s" %(time()-now)
return wrapper
try:
return {"pre":pre_logged,"post":post_logged}[when]
except KeyError, e:
raise ValueError(e),'must be "pre" or "post"'
@logged("post")
def hello(name):
print "Hello,",name
hello("World")
生成器
# coding='utf-8'
def counter(start_at=10):
count = start_at
while(True):
val = (yield count)
if(val is not None):
count = val
else:
count += 1
if(count == 10):
break
for i in counter(3):
print i