如何检查字符串中是否有特定字符(在Python中)

Question

我现在正在为好玩编写一个小系统(用Python编写)。我写邮件检查器时遇到了麻烦。它应该检查电子邮件地址是否包含“.”还有“@”这是代码：

def check_mail(mail):
    email = str(mail)
    needed_charachters = ['@', '.']
    if needed_charachters[1] not in email:
        print(send_error('Mail invalid (has to contain ".")'))
        return False
    if needed_charachters[0] not in email:
        print(send_error('Mail invalid (has to contain "@")'))
        return False
    elif '.' in email:
        print('contains .') 

我已经尝试了一些技巧，但每次都会出现同样的错误。如果我在邮件中输入"ahksdasdhk“，那么我的错误就”必须包含“，”没关系，这是我想要的。“但是当邮件是"gaagsggg@ksdkj.wssf“时，仍然会出现同样的错误。顺便说一下，这是我的错误创建者代码：

def send_error(message):
    return f'ERROR: {message}'

Answer 1

最后一个问题是elif '.'。你可以做这样的事

def check_mail(mail):
    email = str(mail)
    if not email.__contains__("@"):
        print(send_error('Mail invalid (has to contain "@")'))
        return False
    if not email.__contains__("."):
        print(send_error('Mail invalid (has to contain ".")'))
        return False
    # if you passed those steps its valid email so
    return True

或者更简单

def check_mail(mail):
    email = str(mail)
    needed_charachters = ["@", "."]
    err = [x for x in needed_charachters if x not in email]
    err and print(send_error(f"Mail invalid (has to contain '{err[0]}')"))
    return not bool(err)

然而，我自己总是像这样核实电子邮件

import re

regex = """^(\w|\.|\_|\-)+[@](\w|\_|\-|\.)+[.]\w{2,3}$"""
is_valid_email = lambda email: bool(re.search(regex, email))

# checking if email is valid or not
print(is_valid_email("the_email_address@info.com"))

Answer 2

elif是问题所在，请尝试如下：

def check_mail(mail):
    email = str(mail)
    needed_charachters = ['@', '.']
    if needed_charachters[1] not in email:
        print(send_error('Mail invalid (has to contain ".")'))
        return False
    if needed_charachters[0] not in email:
        print(send_error('Mail invalid (has to contain "@")'))
        return False
    else:
        print('Valid mail')
        return True

并建议在循环中这样做：

def check_mail(mail):
    email = str(mail)
    needed_charachters = ['@', '.']
    for character in needed_characters:
        if character not in email:
            print(send_error('Mail invalid (has to contain ' + character + ')'))
            return False        
        else:
            print('Valid mail')
            return True