Python format string

Question

I have this array:

rows = ['1393586700', 'BLAHBLAH', 'BLEHBLEH', '0', '0', '0', '0', '0', '0', '0', '0', '0', '0', '1', '1', '0', '0']

and this format String:

format String:   """%s ,  %s ,  %s ,  %s ,  %s ,  %s ,  %s ,  %s ,  %s ,  %s ,  %s ,  %s ,  %s ,  %s ,  %s ,  %s ,  %s"""

and this fails:

print 'test: ', formatStr % rows

    print 'test: ', formatStr % rows

TypeError: not enough arguments for format string

Why is it failing? there are exactly the same number of %s and fields!

Thanks!

mockinterface · Accepted Answer · 2014-02-28 12:08:18Z

3

This happens because you are printing a list instead of the expected tuple.

Observe this,

>>> print """%s %s""" % [1, 2]
TypeError: not enough arguments for format string

vs.,

>>> print """%s %s""" % (1, 2)
1 2

converting list to a tuple can be done with the tuple() function:

>>> print """%s %s""" % tuple([1, 2])
1 2

answered Feb 28, 2014 at 12:08

mockinterface

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5 Comments

David Villasmil Over a year ago

Hello, Ok, that's clear. Now I'm trying to insert those into mysql and get the same thing, "TypeError: not enough arguments for format string". I see the documentation says it should be an array, and that's what I'm passing.. "rows" is an array... BUT it has only one record, not multiple records...

RemcoGerlich Over a year ago

rows is a list, that's not the same as an array

mockinterface Over a year ago

@DavidVillasmil Python has a special-purpose "C"-like array data type, but one almost always uses lists, and one typically means a list even if talks about an array in python. Are you sure the documentation was talking about an array?

David Villasmil Over a year ago

@mockinterface, not sure, not really... looking at it more carefully it looks like a list of tuples? data = [ ('Jane', date(2005, 2, 12)), ('Joe', date(2006, 5, 23)), ('John', date(2010, 10, 3)), ] stmt = "INSERT INTO employees (first_name, hire_date) VALUES (%s, %s)" cursor.executemany(stmt, data)

David Villasmil Over a year ago

Ok, i finally got it. The idea was to create a list of records (tuples) but as I only had 1 record I ended up with just a list. now, i changed the way i create the array so that for each record I add a tuple to the array, and that works fine for mysql's insert, but of course not for the format string as that's only for 1 record. anyway, thank you for helping me understand!!

Dmitry Zagorulkin · Accepted Answer · 2014-02-28 12:08:44Z

1

You should pass the tuple instead of the list

>>> rows = ['1393586700', 'BLAHBLAH', 'BLEHBLEH', '0', '0', '0', '0', '0', '0', '0', '0', '0', '0', '1', '1', '0', '0']
>>> f = """%s ,  %s ,  %s ,  %s ,  %s ,  %s ,  %s ,  %s ,  %s ,  %s ,  %s ,  %s ,  %s ,  %s ,  %s ,  %s ,  %s"""
>>>
>>> f % tuple(rows) 

'1393586700 ,  BLAHBLAH ,  BLEHBLEH ,  0 ,  0 ,  0 ,  0 ,  0 ,  0 ,  0 ,  0 ,  0 ,  0 ,  1 ,  1 ,  0 ,  0'
    >>>

answered Feb 28, 2014 at 12:08

Dmitry Zagorulkin

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1 Comment

David Villasmil Over a year ago

All right, this worked out perfectly. I wonder why, I am using the same exact procedure to insert in mysql using execute many with multiple rows and that works just fine... Anyway, Thanks!

msvalkon · Accepted Answer · 2014-02-28 12:08:15Z

0

Use str.join

>>> rows = ['1393586700', 'BLAHBLAH', 'BLEHBLEH', '0', '0', '0', '0', '0', '0',
'0', '0', '0', '0', '1', '1', '0', '0']
>>> 
>>> ", ".join(rows)
'1393586700, BLAHBLAH, BLEHBLEH, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0'

answered Feb 28, 2014 at 12:08

msvalkon

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