python254
A. python 中from i import randint i 是什么意思
相当于是取1~254的随机数，然后如果得到的数大于等于170的话，就往后挪1，就达到你要的随机效果了。 a = random.randint(1, 254) if a >= 170: a += 1
B. python 出现路径已存在的错误
这个应该是你的dstDir中已经存在了和你srcDir相同的文件，我也遇到过这个情况
C. Python不能安装ez_setup.py，提示错误,怎么办
需要进入你的python安装路径，更改里面的代码，再次用cmd运行安装命令即可。
D. Python中，我想得到1~255随机整数，用rand.randint(1,255)，但不想让里面170这个数出现，怎么写呢
1、可以使用while函数，对随机进行循环
(4)python254扩展阅读：
除了randint，random模块中比较常用的方法还有：
1、random.random()
生成一个0到1之间的随机浮点数，包括0但不包括1，也就是[0.0, 1.0)。
2、random.uniform(a, b)
生成a、b之间的随机浮点数。不过与randint不同的是，a、b无需是整数，也不用考虑大小。
random.uniform(2.2, 6)
random.uniform(6,2.2)
这两种参数都是可行的。
3、random.choice(seq)
从序列中随机选取一个元素。seq需要是一个序列，比如list、元组、字符串。
random.choice([1, 4, 7, 2, 5, 8]) #list
random.choice('hello') #字符串
random.choice((1, 2, 3)) #元组
都是可行的用法。
E. 如何查看python是否安装成功
直接在命令终端中输入：
1python
如果成功进入python交互式命令行，则安装成功。
如果报如下错：
1command python not found
则可能是环境变量未设置的问题。
F. 怎么样在python多线程实现检测服务器
需要ping一个网段所有机器的在线情况，shell脚步运行时间太长，用python写个多线程ping吧，代码如下：
#!/usr/bin/python
#coding=utf-8
'''
Created on 2015-8-4
@author: Administrator
'''
import threading,subprocess
from time import ctime,sleep,time
import Queue
queue=Queue.Queue()
class ThreadUrl(threading.Thread):
def __init__(self,queue):
threading.Thread.__init__(self)
self.queue=queue
def run(self):
while True:
host=self.queue.get()
ret=subprocess.call('ping -c 1 -w 1 '+host,shell=True,stdout=open('/dev/null','w'))
if ret:
print "%s is down" % host
else:
print "%s is up" % host
self.queue.task_done()
def main():
for i in range(100):
t=ThreadUrl(queue)
t.setDaemon(True)
t.start()
for host in b:
queue.put(host)
queue.join()
a=[]
with open('ip.txt') as f:
for line in f.readlines():
a.append(line.split()[0])
#print a
b=['192.168.3.'+str(x) for x in range(1,254)] #ping 192.168.3 网段
start=time()
main()
print "Elasped Time:%s" % (time()-start)
#t2=threading.Thread(target=move,args=('fff',))
#threads.append(t2)
'''
for i in a:
print ctime()
ping(i)
sleep(1)
if __name__ == '__main__':
for t in range(len(a)):
#t.setDaemon(True)
threads[t].start()
#t.join()
print "All over %s" % ctime()
'''
G. 3进制转换编码（python环境下） 和 36进制转换编码
table={10:'A',11:'B',12:'C',13:'D',14:'E',15:'F'}
foriinrange(10):
table[i]=str(i)
defd2n(decimal_number,n):
"""10进制转其他进制"""
globaltable
max_suppoerted=max(table.keys())+1
assertn<=max_suppoerted,'最大支持%s进制'%max_suppoerted
result=[]
div,mod=divmod(decimal_number,n)
result.append(table[mod])
whilediv>=n:
div,mod=divmod(div,n)
result.append(table[mod])
result.append(table[div])
result.reverse()
print''.join(result)
defn2d(number,n):
"""其他进制转10进制"""
globaltable
reverse_table=dict([(v,k)fork,vintable.items()])
array=list(str(number))
array.reverse()
result=0
fori,xinenumerate(array):
result+=reverse_table[x]*(n**i)
printresult
d2n(254,2)
d2n(254,3)
d2n(254,16)
d2n(254,10)
n2d(100102,3)
n2d('FE',16)结果：
11111110
100102
FE
254
254
254
两个函数组合实现任意两个进制之间的转换
36进制刚好要用完26个字母把table补齐了
H. python函数返回值为”id“：“23”，如何获取23
最近遇到os.system()执行系统命令的情况，上网搜集了一下资料，整理如下，以备不时之需，同时也希望能帮到某些人。
一、python中的 os.system(cmd)的返回值与linux命令返回值（具体参见本文附加内容）的关系
大家都习惯用os.systemv()函数执行linux命令，该函数的返回值十进制数（分别对应一个16位的二进制数）。该函数的返回值与 linux命令返回值两者的转换关系为：该函数的返回值（十进制）转化成16二进制数，截取其高八位（如果低位数是0的情况下，有关操作系统的错误码共 131个，所以低位都是零），然后转乘十进制数即为 linux命令返回值0。
例如：
os.system()返回值为0 linux命令返回值也为0.
os.system()返回值为256，十六位二进制数示为：00000001，00000000，高八位转乘十进制为 1 对应 linux命令返回值 1
os.system()返回值为512，十六位二进制数示为：00000010，00000000，高八位转乘十进制为 2 对应 linux命令返回值 2
......其它同理
os.system()返回值为32512，十六位二进制数示为：01111111，00000000，高八位转乘十进制为 127 对应 linux命令返回值 127
........
/**********************************************************************************************************************/
问题：/bin/xxx.py是一个返回码为1的程序。当python 程序使用os.system(”./bin/xxx.py”) 这样调用的时候， 成功运行后os.system 的返回值出现了问题，变成了256 ，也就是0×100。而不是正常应该返回的1。
解决：查阅了文档发现os.system()的返回为：
On Unix, the return value is the exit status of the process encoded in the format specified for wait().
而os.wait()的返回为：
a 16-bit number, whose low byte is the signal number that killed the process, and whose high byte is the exit status (if the signal number
is zero);
os.system的返回值并不是执行程序的返回结果。而是一个16位的数，它的高位才是返回码。也就是说os.system()返回256即 0×0100，返回码应该是其高位0×01即1。所以要获取程序运行退出的值（比如C的main函数中的return 0），需要处理一下。
ret = os.system('./a.out')
ret >>= 8
这样才能获取到正确的返回值。另外还要注意：python获取到的值是无符号整数，所以返回负值的时候，打印出来是很大的正值。比如返回-1，python 会获取到255，-2则254，以此类推。所以最好就判断是否为0就可以了，实在要判断自己写的c程序返回值，建议返回0,1,2,3等值，出错返回 -1。
另外，我遇到一次明明处理好了返回值，c程序调试信息提示也该返回值0了，结果python获取到的是 -1，而且无论c程序返回多少，python都获取-1。后来排查c程序的问题，发现原来是因为我这个python程序本身是由另一个C程序调用的，而调 用它的那个C程序中将SIGCLD信号忽略了（这表明python是根据子进程退出时产生的信号来获取返回值的），我将那个C程序的SIGCLD绑定到函 数，即使那个函数什么也不做，python也能获取到正确的返回值了。
/**********************************************************************************************************************/
linux命令执行后无论成功与否都有一个返回值：
如果为 0，则表示命令执行成功，其它值则表示错误，具体的错误码含义如下：
"OS error code 1: Operation not permitted"
"OS error code 2: No such file or directory"
"OS error code 3: No such process"
"OS error code 4: Interrupted system call"
"OS error code 5: Input/output error"
"OS error code 6: No such device or address"
"OS error code 7: Argument list too long"
"OS error code 8: Exec format error"
"OS error code 9: Bad file descriptor"
"OS error code 10: No child processes"
"OS error code 11: Resource temporarily unavailable"
"OS error code 12: Cannot allocate memory"
"OS error code 13: Permission denied"
"OS error code 14: Bad address"
"OS error code 15: Block device required"
"OS error code 16: Device or resource busy"
"OS error code 17: File exists"
"OS error code 18: Invalid cross-device link"
"OS error code 19: No such device"
"OS error code 20: Not a directory"
"OS error code 21: Is a directory"
"OS error code 22: Invalid argument"
"OS error code 23: Too many open files in system"
"OS error code 24: Too many open files"
"OS error code 25: Inappropriate ioctl for device"
"OS error code 26: Text file busy"
"OS error code 27: File too large"
"OS error code 28: No space left on device"
"OS error code 29: Illegal seek"
"OS error code 30: Read-only file system"
"OS error code 31: Too many links"
"OS error code 32: Broken pipe"
"OS error code 33: Numerical argument out of domain"
"OS error code 34: Numerical result out of range"
"OS error code 35: Resource deadlock avoided"
"OS error code 36: File name too long"
"OS error code 37: No locks available"
"OS error code 38: Function not implemented"
"OS error code 39: Directory not empty"
"OS error code 40: Too many levels of symbolic links"
"OS error code 42: No message of desired type"
"OS error code 43: Identifier removed"
"OS error code 44: Channel number out of range"
"OS error code 45: Level 2 not synchronized"
"OS error code 46: Level 3 halted"
"OS error code 47: Level 3 reset"
"OS error code 48: Link number out of range"
"OS error code 49: Protocol driver not attached"
"OS error code 50: No CSI structure available"
"OS error code 51: Level 2 halted"
"OS error code 52: Invalid exchange"
"OS error code 53: Invalid request descriptor"
"OS error code 54: Exchange full"
"OS error code 55: No anode"
"OS error code 56: Invalid request code"
"OS error code 57: Invalid slot"
"OS error code 59: Bad font file format"
"OS error code 60: Device not a stream"
"OS error code 61: No data available"
"OS error code 62: Timer expired"
"OS error code 63: Out of streams resources"
"OS error code 64: Machine is not on the network"
"OS error code 65: Package not installed"
"OS error code 66: Object is remote"
"OS error code 67: Link has been severed"
"OS error code 68: Advertise error"
"OS error code 69: Srmount error"
"OS error code 70: Communication error on send"
"OS error code 71: Protocol error"
"OS error code 72: Multihop attempted"
"OS error code 73: RFS specific error"
"OS error code 74: Bad message"
"OS error code 75: Value too large for defined data type"
"OS error code 76: Name not unique on network"
"OS error code 77: File descriptor in bad state"
"OS error code 78: Remote address changed"
"OS error code 79: Can not access a needed shared library"
"OS error code 80: Accessing a corrupted shared library"
"OS error code 81: .lib section in a.out corrupted"
"OS error code 82: Attempting to link in too many shared libraries"
"OS error code 83: Cannot exec a shared library directly"
"OS error code 84: Invalid or incomplete multibyte or wide character"
"OS error code 85: Interrupted system call should be restarted"
"OS error code 86: Streams pipe error"
"OS error code 87: Too many users"
"OS error code 88: Socket operation on non-socket"
"OS error code 89: Destination address required"
"OS error code 90: Message too long"
"OS error code 91: Protocol wrong type for socket"
"OS error code 92: Protocol not available"
"OS error code 93: Protocol not supported"
"OS error code 94: Socket type not supported"
"OS error code 95: Operation not supported"
"OS error code 96: Protocol family not supported"
"OS error code 97: Address family not supported by protocol"
"OS error code 98: Address already in use"
"OS error code 99: Cannot assign requested address"
"OS error code 100: Network is down"
"OS error code 101: Network is unreachable"
"OS error code 102: Network dropped connection on reset"
"OS error code 103: Software caused connection abort"
"OS error code 104: Connection reset by peer"
"OS error code 105: No buffer space available"
"OS error code 106: Transport endpoint is already connected"
"OS error code 107: Transport endpoint is not connected"
"OS error code 108: Cannot send after transport endpoint shutdown"
"OS error code 109: Too many references: cannot splice"
"OS error code 110: Connection timed out"
"OS error code 111: Connection refused"
"OS error code 112: Host is down"
"OS error code 113: No route to host"
"OS error code 114: Operation already in progress"
"OS error code 115: Operation now in progress"
"OS error code 116: Stale NFS file handle"
"OS error code 117: Structure needs cleaning"
"OS error code 118: Not a XENIX named type file"
"OS error code 119: No XENIX semaphores available"
"OS error code 120: Is a named type file"
"OS error code 121: Remote I/O error"
"OS error code 122: Disk quota exceeded"
"OS error code 123: No medium found"
"OS error code 124: Wrong medium type"
"OS error code 125: Operation canceled"
"OS error code 126: Required key not available"
"OS error code 127: Key has expired"
"OS error code 128: Key has been revoked"
"OS error code 129: Key was rejected by service"
"OS error code 130: Owner died"
"OS error code 131: State not recoverable"
I. python中如何用用正则表达式表达251 254这种+3循环的数据
用range 指定步长为3