Python formatting Error (unsupported) [duplicate]

Question

I am building a string with this method. But for some reason I am getting the following error

ValueError: unsupported format character ''' (0x27) at index 38

I have no idea where this is coming from. I checked for typos but nothing.

s = "SELECT %s FROM %s "
data = [colName, tableName]

if whereRoughly:
    s+= "(WHERE "
        for i in range(len(whereRoughly[0])):
            s += "%s LIKE '%%s%' "
            if i+1 < len(whereRoughly[0]): s += "OR "
            data.append(whereRoughly[0][i])
            data.append(whereRoughly[1])
     s+= ")"

s += "ORDER BY %s;"
data.append("desc")

print s
print data
print s % tuple(data)

Here I call all the upper code

s.makeSelect(tableName="students", whereRoughly=([1,2], "Wes"))

This is the actual output

SELECT %s FROM %s (WHERE %s LIKE '%%s%' OR %s LIKE '%%s%' )ORDER BY %s;
['*', 'students', 1, 'Wes', 2, 'Wes', 'desc']

Also, you really, really shouldn't use += on strings in python. You should properly use combinations of format and join. — aruisdante
– aruisdante, Commented May 1, 2014 at 14:34

bgporter · Accepted Answer · 2014-05-01 15:11:46Z

1

The problem is here:

"'%%s%'"

There's no format code %', and trying to use it causes an error.

>>> "'%%s%'" % "foo"
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: unsupported format character ''' (0x27) at index 5

I assume that you're trying to get the SQL LIKE syntax like '%foo%' (enclosed on either side by % and a single quote.

To get that formatting using the old-style % formatting in Python, you need to escape the leading and trailing percents like this:

>>> "'%%%s%%'" % "foo"
"'%foo%'"

(See the docs.)

This is cleaner with modern-style string.format:

>>> "'%{0}%'".format('foo')
"'%foo%'"

(also, the comment above about not using += to build strings is a valid one -- prefer format and join).

edited May 1, 2014 at 15:11

answered May 1, 2014 at 15:01

bgporter

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