我不懂python`print“”“`

Question

I am trying to create a HTML form from a Python CGI script.

script_name=os.environ.get('SCRIPT_NAME', '')

form = cgi.FieldStorage()
message = form.getvalue("message", "(no message)")

print """

  <p>Previous message: %s</p>

  <p>form

  <form method="post" action="%s">
    <p>message: <input type="text" name="message"/></p>
  </form>

</body>

</html>
""" % cgi.escape(message), script_name

The above of course does not work. I was under the false impression that whole print """ blah blah %s ...""" % string_var worked like C's printf function. So what am I suppose to be doing here?

I get this error message in my browser:

Traceback (most recent call last):
  File "/usr/lib/cgi-bin/hello.py", line 45, in <module>
    """ % cgi.escape(message), script_name
TypeError: not enough arguments for format string

Answer 1

print 'blah' % x, y

isn't interpreted as

print 'blah' % (x, y)

but rather as

print ('blah' % x), y

Put parentheses around cgi.escape(message), script_name to pass a tuple as second argument to % . Incidentally, this is one of the reasons you might want to prefer the str.format method over % .

Answer 2

You need to wrap the format arguments in parenthesis.

print """ %s %s
do re me fa so la ti do
""" % (arg1(arg), arg2)

Answer 3

When your code executes, the first thing that happens is it evaluates the expression

long_string % cgi.escape(message)

Because there are two keys in the long string but only one value on the other side of the % operator, this is failing with the TypeError you see.

The solution is to wrap both values in a parentheses, so the second operand is interpreted as a tuple:

long_string % (cgi.escape(message), script_name)