When you merge two indexed dataframes on certain values using 'outer' merge, python/pandas automatically adds Null (NaN) values to the fields it could not match
netbeans-11
decoder
windows-mobile-6
playstation
vms
amf
infobox
nstrackingarea
walletcore
stringstream
quartz.net-2.0
bxslider
rauth
vagrant-share
inertial-navigation
regression
scikits
methodexpression
skip-lists
use-context
website-monitoring
experimental-design
logentries
valums-file-uploader
ckfinder
app-update
drive-mapping
temporal-tables
iterparse
prototype-chain
