python - 赋值前引用的局部变量 X

Question

我尝试使用以下函数连接到 jira，但身份验证错误 401 除外:

def jira_connect(User, Passwd):
try:
    jira = JIRA(basic_auth=(User, Passwd), options={'server': 'https://jira-server-address'})
except JIRAError as e:
    if e.status_code == 401:
        print "Login to JIRA failed. Please check your username and password and try again !"
        exit()
return jira

def main(Thisuser, Thispasswd):
User = Thisuser
Passwd = Thispasswd
jira = jira_connect(User, Passwd)
if __name__== "__main__":
Getuser = getpass.getuser()
Getpasswd = getpass.getpass()
main(Getuser, Getpasswd)

但之后我得到: UnboundLocalError:赋值前引用的局部变量“jira” 这是因为我还应该在 JIRAError 除外的情况下为 jira 变量赋予值吗？因为如果我移动尝试并只是将其作为打击，它就可以正常工作:

def jira_connect(User, Passwd):
    jira = JIRA(basic_auth=(User, Passwd), options={'server': 'https://jira-server-address'})
    return jira

Answer 1

您可以通过在 try block 中包含 return 来实现所需的行为:

def jira_connect(User, Passwd):
    try:
        jira = JIRA(basic_auth=(User, Passwd), options={'server': 'https://jira-server-address'})
        return jira
    except JIRAError as e:
        if e.status_code == 401:
            print "Login to JIRA failed. Please check your username and password and try again !"
            exit()

否则，如果遇到异常，本地变量 jira 在返回时不会被赋值。

否则，您可以在 except block 中分配，例如 jira = None:

def jira_connect(User, Passwd):
    try:
        jira = JIRA(basic_auth=(User, Passwd), options={'server': 'https://jira-server-address'})
    except JIRAError as e:
        if e.status_code == 401:
            print "Login to JIRA failed. Please check your username and password and try again !"
            exit()
        jira = None
    return jira

但我会对此保持警惕，以防状态代码不同于 401 的 JIRAError 导致 None 返回，并且脚本中稍后的代码依赖于在有效的连接上。根据这一点，您可能需要将 exit() 调用放在 if 语句外部的 except block 中。