What is this for an IP in my google app engine log file?

I get many normal log lines in my google app engine application. But today I go these instead the 4-part number:

2a01:e35:2f20:f770:6c54:3ee8:67fb:df8

What is this for an format? ipv6 are 6 numbers, mac address too...

Normal logfile line:

187.14.44.208 - - [19/Mar/2010:14:31:35 -0700] "GET /geo_data.js HTTP/1.1" 200 776 "http://www.xxx.com.br/开发者_JAVA百科spl19/index.php?refid=gv_av_ri" "Mozilla/5.0 (Windows; U; Windows NT 5.1; pt-BR; rv:1.9.2) Gecko/20100115 Firefox/3.6 (.NET CLR 3.5.30729),gzip(gfe)"

This special logfile line:

2a01:e35:2f20:f770:6c54:3ee8:67fb:df8 - - [18/Mar/2010:17:00:37 -0700] "GET /geo_data.js HTTP/1.1" 500 450 "http://www.xxx.com.br/spl19/index.php?refid=cm_av_ri" "Mozilla/5.0 (Windows; U; Windows NT 6.1; pt-PT; rv:1.9.2) Gecko/20100115 Firefox/3.6,gzip(gfe)"

That is IPv6. Your statement that IPv6 addresses have just 6 numbers is incorrect. Here's an IPv6 example next to your address:

2a01 : e35  : 2f20 : f770 : 6c54 : 3ee8 : 67fb : df8  // you
3ffe : 1900 : 4545 : 3    : 200  : f8ff : fe21 : 67cf // example

To the initiated (including me), IPv6 is very confusing.

This is IPv6.

IPv6 numbers are 128-bit numbers normally represented as 8 hex numbers separated by colons, with some abbreviation rules. See Wikipedia IPv6_address.