python学生管理系统id号不能重复典型问题

def generate_gid():
    gids = []
    for number in range(100000, 10000000):
        gids.append(number)
    for gid in gids:
        index0 = random.randint(0, len(gids) - 1)
        index1 = len(gids) - 1
        tmp = gids[index0]
        gids[index0] = gids[index1]
        gids[index1] = tmp
    return gids.pop()

# coding:utf-8
import random
def createRandomString(len):
    print ('wet'.center(10,'*'))
    raw = ""
    range1 = range(58, 65) # between 0~9 and A~Z
    range2 = range(91, 97) # between A~Z and a~z

    i = 0
    while i < len:
        seed = random.randint(48, 122)
        if ((seed in range1) or (seed in range2)):
            continue;
        raw += chr(seed);
        i += 1
    # print(raw)
    return raw

print createRandomString(20)

print ("test".center(20,"-"))
#! coding:utf-8
import uuid
print u"uuid1  生成基于计算机主机ID和当前时间的UUID"
print uuid.uuid1() # UUID('a8098c1a-f86e-11da-bd1a-00112444be1e')

print u"\nuuid3  基于命名空间和一个字符的MD5加密的UUID"
print uuid.uuid3(uuid.NAMESPACE_DNS, 'python.org') #UUID('6fa459ea-ee8a-3ca4-894e-db77e160355e')

print u"\nuuid4  随机生成一个UUID"
print uuid.uuid4()
#'16fd2706-8baf-433b-82eb-8c7fada847da'

print u"\nuuid5  基于命名空间和一个字符的SHA-1加密的UUID"
uuid.uuid5(uuid.NAMESPACE_DNS, 'python.org') #UUID('886313e1-3b8a-5372-9b90-0c9aee199e5d')

print u"\n根据十六进制字符生成UUID"
x = uuid.UUID('{00010203-0405-0607-0809-0a0b0c0d0e0f}')
print u"转换成十六进制的UUID表现字符"
print str(x)       # '00010203-0405-0607-0809-0a0b0c0d0e0f'''