Pandas sum column values according to another columns value

One-liner code to sum Pandas second columns according to same values in the first column.

df2 = df1.groupby(df1.columns[0])[df1.columns[1]].sum().reset_index()

For example, applying to a table listing pipe diameters and lenghts, the command will return total lenghts according to each unique diameters.

This functionality is similar to excel's pivot table sum.

Matplotlib template for Precipitation and Flow over time - Hidrograms and Hyetographs

This code works in python3, to plot a hyetograph - precipitation event (sP), together with a hydrograph (sQ), both in the same time series (t).

#-*-coding:utf-8-*-;
import matplotlib.pyplot as plt
from matplotlib import gridspec
import numpy as np

def plotHH(t,sP,sQ):
    fig = plt.figure()
    gs = gridspec.GridSpec(2, 1, height_ratios=[1, 2])
    
    # HYDROGRAM CHART
    ax = plt.subplot(gs[1])
    ax.plot(t,sQ)
    ax.set_ylabel(u'Q(m³/s)', color='b')
    ax.set_xlabel('Time (min.)')
    ax.tick_params(axis='y', colors='b')
    ax.xaxis.grid(b=True, which='major', color='.7', linestyle='-')
    ax.yaxis.grid(b=True, which='major', color='.7', linestyle='-')
    ax.set_xlim(min(t), max(t))
    ax.set_ylim(0, max(sQ)*1.2)

    # PRECIPITATION/HYETOGRAPH CHART
    ax2 = plt.subplot(gs[0])
    ax2.bar(t, sP, 1, color='#b0c4de')
    ax2.xaxis.grid(b=True, which='major', color='.7', linestyle='-')
    ax2.yaxis.grid(b=True, which='major', color='0.7', linestyle='-')
    ax2.set_ylabel('P(mm)')
    ax2.set_xlim(min(t), max(t))
    plt.setp(ax2.get_xticklabels(), visible=False)
    
    plt.tight_layout()
    ax2.invert_yaxis()
    plt.gcf().subplots_adjust(bottom=0.15)
    plt.show()
    #plt.savefig(filename,format='pdf')
    plt.close(fig)