trip_count_by_month=trip.groupby(['start_Year','start_Month'])['id'].count().reset_index()

trace1 = go.Bar(
    x=trip_count_by_month.start_Month.astype(str)+'-'+trip_count_by_month.start_Year.astype(str),
    y=trip_count_by_month.id,
    name='No. of trips',
    marker=dict(
        color=chosen_colors[0]
    )
)

data=[trace1]

layout = go.Layout(
    title='No. of bike trips by month',
    xaxis=dict(
        title='Month'
    ),
    yaxis=dict(
        title='No. of bike trips'
    ),
)

figure = go.Figure(data=data, layout=layout)

ply.iplot(figure)