Python - How to concatenate Strings and Integers in Python?

Question

I'm with some trouble getting this code to work:

count_bicycleadcategory = 0
for item_bicycleadcategory in some_list_with_integers:
    exec 'model_bicycleadcategory_%s.bicycleadcategorytype = BicycleAdCategoryType.objects.get(pk=' + str(item_bicycleadcategory) + ')' % count_bicycleadcategory
    count_bicycleadcategory = count_bicycleadcategory + 1

I'm getting an error:

Type Error, not all arguments converted during string formatting

My question is: Any clue on how I pass the "item_bicycleadcategory" to the exec expression?

Best Regards,

Answer 1

You are already using python's format syntax:

"string: %s\ndecimal: %d\nfloat: %f" % ("hello", 123, 23.45)

More info here: http://docs.python.org/2/library/string.html#format-string-syntax

Answer 2

First, exec is even more dangerous than eval() , so be absolutely sure that your input is coming from a trusted source. Even then, you shouldn't do it. It looks like you're using a web framework or something of the sort, so really don't do it!

The problem is this:

exec 'model_bicycleadcategory_%s.bicycleadcategorytype = BicycleAdCategoryType.objects.get(pk=' + str(item_bicycleadcategory) + ')' % count_bicycleadcategory

Take a closer look. You're trying to put the string formatting argument to a single parentesis with no format strings with ')' % count_bicycleadcategory .

You could do this:

exec 'model_bicycleadcategory_%s.bicycleadcategorytype = BicycleAdCategoryType.objects.get(pk=' % count_bicycleadcategory + str(item_bicycleadcategory) + ')' 

But what you really should be doing is not using exec at all !

Create a list of your model instances and use that instead.

Answer 3

for python 2.7 you could use format:

string = '{0} give me {1} beer'
string.format('Please', 3)

out:

Please give me 3 beer

you could do many things with format , for example:

string = '{0} give me {1} {0} beer'

out:

Please give me 3 Please beer.

Answer 4

try this :

exec 'model_bicycleadcategory_%s.bicycleadcategorytype = BicycleAdCategoryType.objects.get(pk=%s)' % (count_bicycleadcategory, str(item_bicycleadcategory))

(you mustn't mix %s and string + concatenation at the same time)

Answer 5

尝试这个：

exec 'model_bicycleadcategory_%d.bicycleadcategorytype = BicycleAdCategoryType.objects.get(pk=%d)' % (count_bicycleadcategory, item_bicycleadcategory)