python2.7多线程锁相关的问题，求解

Question

本人大学生一枚，不是很懂python，为什么代码单独跑能行，封装成函数之后传值就有问题了，是多线程锁相关的问题吗？求解答

import socket, time, thread,os

socket.setdefaulttimeout(3)


def socket_port(ip, port):
    """
    输入IP和端口号，扫描判断端口是否开放
    """
    try:
        if port >= 65535:
            print u'端口扫描结束'
        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        result = s.connect_ex((ip, port))
        if result == 0:
            lock.acquire()
            print ip, u':', port, u'端口开放'
            try:
                print port
                sqlAdd = 'insert into portsscan(port)VALUES ("%s;")' % port
                cursor.execute(sqlAdd)
                db.commit()
            except Exception, e:
                print'2', e
            lock.release()
        s.close()
    except:
        print u'端口扫描异常'


def ip_scan(ip):
    """
    输入IP，扫描IP的0-65534端口情况
    """
    try:
        print u'开始扫描 %s' % ip
        start_time = time.time()
        for i in range(0, 65534):
            thread.start_new_thread(socket_port, (ip, int(i)))
        print u'扫描端口完成，总共用时 ：%.2f' % (time.time() - start_time)
        raw_input("Press Enter to Exit")
    except:
        print u'扫描ip出错'

import pymysql
def main(url):
    global db,cursor
    try:
        db=pymysql.connect('localhost','root','root','test')
        cursor=db.cursor()
        sqlDelete='delete from portsscan'
        cursor.execute(sqlDelete)
        db.commit()
    except Exception,e:
        print '1',e
    lock = thread.allocate_lock()
    ip_scan(url)
    db.close()
    return

target='192.168.242.189'
main(target)

#这下面能正常运行，而上面封装函数运行就不行
a='192.168.242.189'
global db,cursor
try:
    db=pymysql.connect('localhost','root','root','test')
    cursor=db.cursor()
    sqlDelete='delete from portsscan'
    cursor.execute(sqlDelete)
    db.commit()
except Exception,e:
    print '1',e
lock = thread.allocate_lock()
ip_scan(a)
db.close()

Answer 1

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在你的代码中，问题主要出现在全局变量管理和多线程同步上。为了解决这个问题，我们可以将数据库连接、游标和锁作为参数传递给函数，这样每个线程都可以独立管理它们，并且避免了全局变量导致的潜在竞争条件。

下面是修改后的代码：

import socket
import time
import threading
import os
import pymysql

socket.setdefaulttimeout(3)

def socket_port(db, cursor, lock, ip, port):
    """
    输入IP和端口号，扫描判断端口是否开放
    """
    try:
        if port >= 65535:
            print(u'端口扫描结束')
        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        result = s.connect_ex((ip, port))
        if result == 0:
            lock.acquire()
            print(ip, u':', port, u'端口开放')
            try:
                print(port)
                sqlAdd = 'INSERT INTO portsscan(port) VALUES ("%s";)' % port
                cursor.execute(sqlAdd)
                db.commit()
            except Exception as e:
                print('2', e)
            lock.release()
        s.close()
    except:
        print(u'端口扫描异常')


def ip_scan(db, cursor, lock, ip):
    """
    输入IP，扫描IP的0-65534端口情况
    """
    try:
        print(u'开始扫描 %s' % ip)
        start_time = time.time()
        threads = []
        for i in range(0, 65534):
            t = threading.Thread(target=socket_port, args=(db, cursor, lock, ip, i))
            threads.append(t)
            t.start()

        for t in threads:
            t.join()

        print(u'扫描端口完成，总共用时 ：%.2f' % (time.time() - start_time))
        input("Press Enter to Exit")
    except:
        print(u'扫描ip出错')

def main(url):
    try:
        db = pymysql.connect('localhost', 'root', 'root', 'test')
        cursor = db.cursor()
        sqlDelete = 'DELETE FROM portsscan'
        cursor.execute(sqlDelete)
        db.commit()
    except Exception as e:
        print('1', e)
    lock = threading.Lock()
    ip_scan(db, cursor, lock, url)
    db.close()

target = '192.168.242.189'
main(target)

这段代码做了以下改进：

1. 将数据库连接、游标和锁作为参数传递给ip_scan()和socket_port()函数。
2. 使用threading.Thread替换thread.start_new_thread，这是Python 2.7中的推荐做法。
3. 在ip_scan()中，创建一个列表存储所有线程并调用t.start()启动它们。然后遍历线程列表并调用t.join()等待所有线程完成。

现在，这个版本应该可以正确地处理多线程并发访问数据库的情况。同时，它也避免了使用全局变量带来的潜在问题。