检查python中两个函数的字符串是否为真（字符串操作）

我有下面的代码，虽然它只用于检查一个函数（比如小写），但当引入两个条件时，它就会停止工作。是否有人能为教学目的提供一些线索，解释为什么会出现这种情况，给出解决方案，并解释理由。注意：这不是任何其他问题的重复，因为其他示例没有显式处理字符串布尔命令

预期结果：仅当用户名输入为小写且包含数字时，才应生成电子邮件地址。（例如，username123可接受，USER不可接受，USER123不可接受）

解决方案/答案必须简单，理想情况下不包括代码重写（即不重写函数和引入参数等，如果可能的话）

代码：

def main():
   print("*************************** Create an e-mail address*********************")
   print("***************************                                               ********************** ")

   username=input("Please enter your desired username:" )

   if username.islower() and username.isdigit():
         email=username+"@gmail.com"
         print("Your unique email address is now:", email)
   else:
         print("Your username needs to be lower case ...............")
         main()

main()

*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:USER
Your username needs to be lower case ...............
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:user
Your unique email address is now: user@gmail.com
>>> 

*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:USER
Your username needs to be lower case ...............
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:user
Your username needs to be lower case ...............
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:user123
Your username needs to be lower case ...............
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:

def main():
   print("*************************** Create an e-mail address*********************")
   print("***************************                                               ********************** ")
   username=input("Please enter your desired username:" )
   if username.islower() and username.isdigit():
         email=username+"@gmail.com"
         print("Your unique email address is now:", email)
   else:
         print("Your username needs to be lower case and contain digits...............")
main()

Please enter your desired username:USERNAME
Your username needs to be lower case and contain digits...............
>>> main()
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:username123
Your username needs to be lower case and contain digits...............
>>> 

def main():
   print("*************************** Create an e-mail address*********************")
   print("***************************                                               ********************** ")
   username=input("Please enter your desired username:" )
   #if username.islower() or username.isdigit():
   if username.islower() and set(range(10)).intersection(username):
         email=username+"@gmail.com"
         print("Your unique email address is now:", email)
   else:
         print("Your username needs to be lower case and contain digits...............")
main()

如前所述，下面的代码（仅检查孤岛者）工作正常

   if username.islower():
         email=username+"@gmail.com"
         print("Your unique email address is now:", email)
   else:
         print("Your username needs to be lower case ...............")
         main()

工作输出：

def main():
   print("*************************** Create an e-mail address*********************")
   print("***************************                                               ********************** ")

   username=input("Please enter your desired username:" )

   if username.islower() and username.isdigit():
         email=username+"@gmail.com"
         print("Your unique email address is now:", email)
   else:
         print("Your username needs to be lower case ...............")
         main()

main()

*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:USER
Your username needs to be lower case ...............
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:user
Your unique email address is now: user@gmail.com
>>> 

*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:USER
Your username needs to be lower case ...............
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:user
Your username needs to be lower case ...............
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:user123
Your username needs to be lower case ...............
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:

def main():
   print("*************************** Create an e-mail address*********************")
   print("***************************                                               ********************** ")
   username=input("Please enter your desired username:" )
   if username.islower() and username.isdigit():
         email=username+"@gmail.com"
         print("Your unique email address is now:", email)
   else:
         print("Your username needs to be lower case and contain digits...............")
main()

Please enter your desired username:USERNAME
Your username needs to be lower case and contain digits...............
>>> main()
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:username123
Your username needs to be lower case and contain digits...............
>>> 

def main():
   print("*************************** Create an e-mail address*********************")
   print("***************************                                               ********************** ")
   username=input("Please enter your desired username:" )
   #if username.islower() or username.isdigit():
   if username.islower() and set(range(10)).intersection(username):
         email=username+"@gmail.com"
         print("Your unique email address is now:", email)
   else:
         print("Your username needs to be lower case and contain digits...............")
main()

更新： 有人认为这是由于缺少（），但事实并非如此：

def main():
   print("*************************** Create an e-mail address*********************")
   print("***************************                                               ********************** ")

   username=input("Please enter your desired username:" )
   if username.islower() and username.isdigit():
         email=username+"@gmail.com"
         print("Your unique email address is now:", email)
   else:
         print("Your username needs to be lower case ...............")
         main()
main()

输出错误：

def main():
   print("*************************** Create an e-mail address*********************")
   print("***************************                                               ********************** ")

   username=input("Please enter your desired username:" )

   if username.islower() and username.isdigit():
         email=username+"@gmail.com"
         print("Your unique email address is now:", email)
   else:
         print("Your username needs to be lower case ...............")
         main()

main()

*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:USER
Your username needs to be lower case ...............
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:user
Your unique email address is now: user@gmail.com
>>> 

*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:USER
Your username needs to be lower case ...............
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:user
Your username needs to be lower case ...............
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:user123
Your username needs to be lower case ...............
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:

def main():
   print("*************************** Create an e-mail address*********************")
   print("***************************                                               ********************** ")
   username=input("Please enter your desired username:" )
   if username.islower() and username.isdigit():
         email=username+"@gmail.com"
         print("Your unique email address is now:", email)
   else:
         print("Your username needs to be lower case and contain digits...............")
main()

Please enter your desired username:USERNAME
Your username needs to be lower case and contain digits...............
>>> main()
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:username123
Your username needs to be lower case and contain digits...............
>>> 

def main():
   print("*************************** Create an e-mail address*********************")
   print("***************************                                               ********************** ")
   username=input("Please enter your desired username:" )
   #if username.islower() or username.isdigit():
   if username.islower() and set(range(10)).intersection(username):
         email=username+"@gmail.com"
         print("Your unique email address is now:", email)
   else:
         print("Your username needs to be lower case and contain digits...............")
main()

删除递归main（）调用也不会改变任何事情：

def main():
   print("*************************** Create an e-mail address*********************")
   print("***************************                                               ********************** ")

   username=input("Please enter your desired username:" )

   if username.islower() and username.isdigit():
         email=username+"@gmail.com"
         print("Your unique email address is now:", email)
   else:
         print("Your username needs to be lower case ...............")
         main()

main()

*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:USER
Your username needs to be lower case ...............
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:user
Your unique email address is now: user@gmail.com
>>> 

*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:USER
Your username needs to be lower case ...............
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:user
Your username needs to be lower case ...............
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:user123
Your username needs to be lower case ...............
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:

def main():
   print("*************************** Create an e-mail address*********************")
   print("***************************                                               ********************** ")
   username=input("Please enter your desired username:" )
   if username.islower() and username.isdigit():
         email=username+"@gmail.com"
         print("Your unique email address is now:", email)
   else:
         print("Your username needs to be lower case and contain digits...............")
main()

Please enter your desired username:USERNAME
Your username needs to be lower case and contain digits...............
>>> main()
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:username123
Your username needs to be lower case and contain digits...............
>>> 

def main():
   print("*************************** Create an e-mail address*********************")
   print("***************************                                               ********************** ")
   username=input("Please enter your desired username:" )
   #if username.islower() or username.isdigit():
   if username.islower() and set(range(10)).intersection(username):
         email=username+"@gmail.com"
         print("Your unique email address is now:", email)
   else:
         print("Your username needs to be lower case and contain digits...............")
main()

输出错误：

def main():
   print("*************************** Create an e-mail address*********************")
   print("***************************                                               ********************** ")

   username=input("Please enter your desired username:" )

   if username.islower() and username.isdigit():
         email=username+"@gmail.com"
         print("Your unique email address is now:", email)
   else:
         print("Your username needs to be lower case ...............")
         main()

main()

*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:USER
Your username needs to be lower case ...............
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:user
Your unique email address is now: user@gmail.com
>>> 

*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:USER
Your username needs to be lower case ...............
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:user
Your username needs to be lower case ...............
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:user123
Your username needs to be lower case ...............
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:

def main():
   print("*************************** Create an e-mail address*********************")
   print("***************************                                               ********************** ")
   username=input("Please enter your desired username:" )
   if username.islower() and username.isdigit():
         email=username+"@gmail.com"
         print("Your unique email address is now:", email)
   else:
         print("Your username needs to be lower case and contain digits...............")
main()

Please enter your desired username:USERNAME
Your username needs to be lower case and contain digits...............
>>> main()
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:username123
Your username needs to be lower case and contain digits...............
>>> 

def main():
   print("*************************** Create an e-mail address*********************")
   print("***************************                                               ********************** ")
   username=input("Please enter your desired username:" )
   #if username.islower() or username.isdigit():
   if username.islower() and set(range(10)).intersection(username):
         email=username+"@gmail.com"
         print("Your unique email address is now:", email)
   else:
         print("Your username needs to be lower case and contain digits...............")
main()

使用或代替，并且也不起作用

当更改为或时，输出如下

Please enter your desired username:USERNAME
Your username needs to be lower case and contain digits...............
>>> main()
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:username
Your unique email address is now: username@gmail.com
>>> 

使用集合（范围（10））尝试下面的另一个建议答案。交叉点：

以下内容-仍不工作：

def main():
   print("*************************** Create an e-mail address*********************")
   print("***************************                                               ********************** ")

   username=input("Please enter your desired username:" )

   if username.islower() and username.isdigit():
         email=username+"@gmail.com"
         print("Your unique email address is now:", email)
   else:
         print("Your username needs to be lower case ...............")
         main()

main()

*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:USER
Your username needs to be lower case ...............
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:user
Your unique email address is now: user@gmail.com
>>> 

*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:USER
Your username needs to be lower case ...............
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:user
Your username needs to be lower case ...............
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:user123
Your username needs to be lower case ...............
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:

def main():
   print("*************************** Create an e-mail address*********************")
   print("***************************                                               ********************** ")
   username=input("Please enter your desired username:" )
   if username.islower() and username.isdigit():
         email=username+"@gmail.com"
         print("Your unique email address is now:", email)
   else:
         print("Your username needs to be lower case and contain digits...............")
main()

Please enter your desired username:USERNAME
Your username needs to be lower case and contain digits...............
>>> main()
*************************** Create an e-mail address*********************
***************************                                               ********************** 
Please enter your desired username:username123
Your username needs to be lower case and contain digits...............
>>> 

def main():
   print("*************************** Create an e-mail address*********************")
   print("***************************                                               ********************** ")
   username=input("Please enter your desired username:" )
   #if username.islower() or username.isdigit():
   if username.islower() and set(range(10)).intersection(username):
         email=username+"@gmail.com"
         print("Your unique email address is now:", email)
   else:
         print("Your username needs to be lower case and contain digits...............")
main()

输出

  >>> main()
    *************************** Create an e-mail address*********************
    ***************************                                               ********************** 
    Please enter your desired username:user
    Your username needs to be lower case and contain digits...............
    >>> main()
    *************************** Create an e-mail address*********************
    ***************************                                               ********************** 
    Please enter your desired username:username123
    Your username needs to be lower case and contain digits...............
    >>> 

---

您可以创建一个简单的函数

def hasNumbers(inputString):
      return any(char.isdigit() for char in inputString)
.
.
.
if username.islower() and hasNumbers(username):
.
.
.

然后在if语句中使用它。这是我从中找到它的源：。 如果愿意，还可以使用正则表达式，使用re模块。但是对于像这样小的东西，我建议你使用一个单独的函数。这是一个更简单的解决方案

正则表达式版本：

import re

def main():
   print("*************************** Create an e-mail address*********************")
   print("***************************                                               ********************** ")

   username=str(input("Please enter your desired username:" ))

   pat = re.compile(r'\d')

   if username.islower() and re.search(pat, username):
         email=username+"@gmail.com"
         print("Your unique email address is now:", email)
   else:
         print("Your username needs to be lower case ...............")
         main()

main()

---

这条线的问题

如果username.islower（）和username.isdigit（）

就是说，

isdigit（）

仅当整个字符串为数字时返回True，而

islower（）

显然仅当整个字符串为小写字符时返回True。这意味着该语句将始终失败，因为这两个条件都不可能为真

如果我们重新考虑一下逻辑，我们需要测试的是电子邮件只包含字母数字字符（数字和字母），但不包含任何大写字母。这给了我们：

---

if username.isalnum（）和（不是任何（c.isupper（）表示用户名中的c）

有人说，代码的问题是如果执行

username.isdigit（）

它返回

False

语句，因为变量username没有完全用数字填充，但是，

islower（）

没有那么严格：

username = input(' -->> ')
-->> abc123

username.isdigit()

假的

真的

在您的特定情况下，如果有大写字母，您可以忽略警告，因为您可以将它们转换为小写。如果您需要一个同时检查大写字母的解决方案，那么您还应该阅读结尾的附加部分。

如果用户名的结构没有真正困扰您，即您只是希望它同时包含小写字母和数字，那么您可以使用以下方法检查它们是否都存在：

例如，即使

username='A1b2C3'

，它也能很好地工作

---

但是，如果结构很重要，并且您希望不惜任何代价让数字跟在字母后面，则应将用户名分为两个子集，一个包含字母，另一个包含数字，并检查两者的顺序是否正确。请注意，这只是一种个人方法：

• 首先，我们检查用户名是否可以将其连续分成两组字母和数字，不能多也不能少

• 其次，我们检查第一个子集是否包含字母，第二个子集是否包含数字

• 如果满足条件，则我们创建一封电子邮件

代码应如下所示：

import re

print('Example of username: george1337')
username = 'Abc123'; username = username.lower()

if len(re.findall('\d+|\D+', username)) == 2:
    subset_1, subset_2 = [subset for subset in re.findall('\d+|\D+', username)]
else:
    print('Not valid username: see example')

if subset_1.islower() and subset_2.isdigit():
    email = username + '@gmail.com'
    print('Your e-mail address is: {}'.format(email))
else:
    print('Digits must follow letters, not vice versa')

您的电子邮件地址是：abc123@gmail.com

无效用户名：请参见示例

---

附加部分 好的。如果您希望在有大写字母时发出警告，则不应执行

username=username.lower（）

。在第二部分中会自动检查“大写条件”，因为有

If subset_1.islower（）

。然后只需添加另一个

打印

，指示不允许使用大写字母。第一部分也是如此

---

我希望这会有所帮助！

在第一个示例中，您忘记了islower（）函数调用的括号。很抱歉，我在代码中添加了括号。这是在原始代码中-并且不起作用。请运行它并查看-！您的第一个代码段是递归的；您在

main（）中调用
main（）
Chris，是的，但是删除它并不能解决问题（请参见更新）’和username.isdigit（）’…“user”对此是错误的。您的意思是“and not username.isdigit（）”，并要求双方都计算为true将其更改为“or”而不是“and”也不起作用。请参阅使用输出编辑取决于OP是否打算允许数字用户名：如果不打算将数字用作用户名，则第二部分需要not运算符。我同意。我正在尝试找出他真正想要的输出。哦，我现在明白了。他希望用户名包含小写字母和数字。此链接：使用函数
def hasNumbers（inputString）：返回any（inputString中char的char.isdigit（））
并使用传递字符串的函数作为参数。然后，您只需更改错误消息。抱歉，*