typeError: not all arguments convereted during string formatting

Question

I have a function as follows (I am working on python2.7):

def ip_split(ip):

    rtr, mask = cidr.split('/')                                                  
    ip = ipaddress.ip_address(unicode(rtr))                                      
    if ip.version == 4:                                                          
        n = ipaddress.IPv4Network(unicode(cidr), strict=False)                   
    else:                                                                        
        n = ipaddress.IPv6Network(unicode(cidr), strict=False)                   
    first, last = n[2], n[-2]                                                    
    return n, first, last, n[1], n.network_address, mask 

n_sub = "%s/%s" % ip_split('10.10.128.1/18')[3:]

Traceback (most recent call last):
  File "python", line 18, in <module>
TypeError: not all arguments converted during string formatting

I am getting the typeError: not all arguments convereted during string formatting.

What can be wrong over here??

Answer 1

Your ip_split function returns a 6-tuple. If you use the [3:] slice operator, you will obtain everything from index 3 and further, so that will be a 3-tuple.

But your formatting string '%s/%s' has only two %ss, so Python gets confused. You can (probably) fix it with slicing from index four, so [4:].

A second problem is that % takes precedence over indexing, so it sees the expression as ('%s/%s' % ip_split('10.10.128.1/18'))[3:], whereas I think you want to first get the last two items of the tuple. The fact that you uses spaces here does not makes a difference (yes, for scoping, Python takes spaces into account, but not for operator precedence).

Alternatively, you can use [-2:], which is closer to "the last two items". So:

n_sub = "%s/%s" % (ip_split('10.10.128.1/18')[-2:])