Yubin Ruan wrote: > Hi, everyone, I have some problem understand the rule which the python > compiler use to parsing the multiline string. > > Consider this snippet: > > str_1 = "foo" > str_2 = "bar" > > print "A test case" + \ > "str_1[%s] " + \ > "str_2[%s] " % (str_1, str_2) > > Why would the snippet above give me an "TypeError: not all arguments > converted during string formatting" while the one below not ? > > print "A test case" + \ > "str_1[%s] " % str1 > > Obviously the first snippet have just one more line and one more argument > to format than the second one. Isn't that unreasonable ? I couldn't find > any clue about that. Anyone help ? > > I am using python 2.7.6 >
It doesn't matter into how many lines you break your statement. The % operator has higher precedence than +, so a + b % c is evaluated as a + (b % c). When c is a 2-tuple and b contains only one "%s" that inevitably fails: >>> "%s" + "%s" % (1, 2) Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: not all arguments converted during string formatting > Also, I know the **Pythonic** way to play with multiline, which would be > using triple quote or a pair of parenthesis to surround the multiline > string to make it a **online** string. You don't have to show code in that > respect. Did you know that adjacent string literals are merged into one? Compare: >>> print "foo" + \ ... "%s" + \ ... "%s" % (1, 2) Traceback (most recent call last): File "<stdin>", line 3, in <module> TypeError: not all arguments converted during string formatting >>> print "foo" \ ... "%s" \ ... "%s" % (1, 2) foo12 -- https://mail.python.org/mailman/listinfo/python-list
