python - Using Merge on a column and Index in Pandas -

i have 2 separate dataframes share project number. in type_df, project number index. in 'time_df', project number column. count number of rows in type_df have project type of 2. trying pandas.merge(). works great when using both columns, not indices. i'm not sure how reference index , if merge right way this.

import pandas pd type_df = pd.dataframe(data = [['type 1'], ['type 2']], columns=['project type'], index=['project2', 'project1']) time_df = pd.dataframe(data = [['project1', 13], ['project1', 12], ['project2', 41]], columns=['project', 'time'])  merged = pd.merge(time_df,type_df, on=[index,'project']) print merged[merged['project type'] == 'type 2']['project type'].count() 

error:

name 'index' not defined. 

desired output:

2 

if want use index in merge have specify left_index=true or right_index=true, , use left_on or right_on. should this:

merged = pd.merge(type_df,time_df, left_index = true, right_on='project')