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I am experimenting some string outputs and I came across something that throws an error when printing

x = "ll=%s%2C%20%s" % ("lat", "lng")

The syntax above throws an error:

ValueError: unsupported format character 'C' (0x43) at index 7

What am I missing here? I wish to have a result of:

ll=lat%2C%20lang

With the use of %s operators on concatenating a variable inside a string

Dean Christian Armada
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4 Answers4

8

When python sees that %, it's expecting a formatting symbol right afterwards. Basically, it expects something like %s or %d... But it finds a C, and it doesn't know what to do with that.

You can see what can you put after the % in this link.

If you want to have literally % in your string you have to escape it with another %:

>>> x = "ll=%s%%2C%%20%s" % ("lat", "lng")
>>> x
'll=lat%2C%20lng'

Note that in Python 3, this way is considered "outdated" in favor of the newer .format() method. You can also use that one in Python 2.7 (I believe, though I'm not sure that it was introduced in Python 2.6 ?) and do the same like this:

>>> x = "ll={0}%2C%20{1}".format("lat", "lng")
>>> x
'll=lat%2C%20lng'

Or you could do even fancier things:

>>> x = "ll={latitude}%2C%20{longitude}".format(latitude="lat", longitude="lng")
>>> x
'll=lat%2C%20lng'

Check it out! (also, there's a Reddit thread about it)

Savir
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2

First of all if you want to print % you need to do it like this

%% --> escapes the % literal character

every other combinations will be treated as formatted characters. for example %c is treated as a single character, represented as a C int.

Please refer to the link here

idjaw
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Ajay Pal
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2

To escape the % in python, just use %%, in your example, the following will give the result you want, 

x = "ll=%s%%2C%%20%s" % ("lat", "lng")

Or you could use string's format method which is preferred in python 3 and also available in python 2.7

x = "ll={0:s}%2C%20{1:s}".format("lat", "lng")

One tip for you to transit from % style formatting to string's format method, AFAIK, all % format letters remain the same used in string's format method. This means "%s" % "lat" would simply become "{0:s}".format("lat"), "%d" % 3 to "{0:d}".format(3), and etc. Notice the 0 here. It indicates which parameter in the format method is formatted, with first parameter indexed as 0.

See more details here on the official documentation about python string's format method

ilnahz
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    Congrats on contributing your first answer! :) Just a friendly note to make use of the formatting tools when answering questions. I took the liberty to edit your answer to format it accordingly. But if you go back in to editing your answer, you will see some tools available to help format your answer. :) Cheers. – idjaw Oct 25 '16 at 02:58
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    Thanks a lot for the tips, @idjaw! just notice the use of markdown syntax here! – ilnahz Oct 25 '16 at 03:01
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aside from % escape. you can also add the '%' in the 'lat' before passing it or just add another '%s' for '%'

>>> x = "ll=%s2C%s20%s" % ("lat%", "%","lng")
>>> x
'll=lat%2C%20lng'

im just giving you another option.but %% escape is the best choice

Randy Arguelles
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