记一段python parameter **kwargs出错的问题

下面是可以运行的代码。

import smtplib
from email.mime.text import MIMEText
from email.mime.base import MIMEBase
from email.mime.multipart import MIMEMultipart

from email.utils import COMMASPACE,formatdate
from email import encoders

#charset.add_charset('utf-8', charset.QP, charset.QP)
def my_send_mail(subject,message,from_addr,*to_addrs,headers):
    email=MIMEText(message,"plain",_charset="utf-8")
    #email=MIMEMultipart()
    assert type(headers)==dict
    email['subject']=subject
    email['From']=from_addr
    headers=headers.copy()
    for (header,value) in headers.items():
        email[header]=value

    host="localhost"
    port=1025
    sender=smtplib.SMTP(host,port)
    for addr in to_addrs:
        del email['To']
        email['To']=addr
        email['Date']=formatdate(localtime=True)

        sender.sendmail(from_addr,addr,email.as_string())
    sender.quit()


headers={"Reply-To":"[e-mail]"}
my_send_mail("A model subject","The message contents","[e-mail]","[e-mail]","[e-mail]",headers=headers)

下面这段代码也能执行，但是关键在于调用的方式。

def send_mail(subject,message,from_addr,*to_addrs,**headers):
    email=MIMEText(message,"plain",_charset="utf-8")
    #email=MIMEMultipart()
    assert type(headers)==dict
    email['subject']=subject
    email['From']=from_addr
    headers=headers.copy()
    for (header,value) in headers.items():
        email[header]=value

    host="localhost"
    port=1025
    sender=smtplib.SMTP(host,port)
    for addr in to_addrs:
        del email['To']
        email['To']=addr
        email['Date']=formatdate(localtime=True)

        sender.sendmail(from_addr,addr,email.as_string())
    sender.quit()

可以执行的调用：

send_mail("A model subject","The message contents","[e-mail]","[e-mail]","[e-mail]",**{'Reply-To':'[e-mail]'})

不能执行的调用：

send_mail("A model subject","The message contents","[e-mail]","[e-mail]","[e-mail]",'Reply-To'='[e-mail]')
                                                                                                             ^
SyntaxError: keyword can't be an expression

这个报错有点像这个：

>>> d1={1:"one"}
>>> d2={"1":"one"}
>>> a=dict(1="one")
  File "", line 1
SyntaxError: keyword can't be an expression
>>> b=dict("1"="one")
  File "", line 1
SyntaxError: keyword can't be an expression

参考python 发送邮件的代码：
http://blog.csdn.net/menglei8625/article/details/7721746