How do you stack a bar chart in Matlibplot using a loop

Here is a description: https://matplotlib.org/3.1.3/gallery/lines_bars_and_markers/bar_stacked.html#sphx-glr-gallery-lines-bars-and-markers-bar-stacked-py


You only present half of the code (imports statements are missing)
Also valid sample data is missing... Can you provide these?

import numpy as np
import sys
import matplotlib.pyplot as plt
import pandas as pd
from datetime import timedelta as td


sample = ['Test1', 'Test2']
# the value is timedelta dataframe
evDict = {'Test1':[Timedelta('0 days 05:08:28'),Timedelta('0 days 03:08:28')],
           'Test2':[Timedelta('0 days 05:08:28'),Timedelta('0 days 03:08:28')]}


N =2
ind = np.arange(N)

stacker = 0
for idx, ev in enumerate(sample):
      
    r = [int(t.seconds/3600) for t in evDict[ev]]
    if idx ==0:
        plt.bar(ind, r)
        stacker = r
    else:
         plt.bar(ind, r, bottom=stacker)
         stacker = r

plt.show

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What are the modules for np & plt. The imports are still missing, TImedelta is an unknown function from what library does that get imported.
the datetime module has a timedelta that does not accept strings as parameter.
the standard numpy has no arrange() function.

Updated above

Please try again at a working reproducer.

run python yourscript from a command line: until it shows no more errors please.

Hints:
dataframe is an unknown module,
np.arrange() probably needs to be np.arange()
there is an ) missing in the expression r = .....    
evDict has no names... how to refer to evDict[ev].duration

Updated

import numpy as np
import sys
import matplotlib.pyplot as plt
import pandas as pd
from datetime import timedelta as td

class Sample:
    def __init__(self, name, tasks, duration):
        self.name = name
        self.tasks = tasks
        self.duration = duration

df = pd.read_excel('sample.xlsx')
print(df)

sampleDict = {}
for ev in df.Sample.unique():
    dur = []
    for tsk in df.Tasks.unique():
        dur.append(df.query('Tasks == "%s" and Sample == "%s"' %(tsk, ev))['End Date'].max() - 
                   df.query('Tasks == "%s" and Sample == "%s"' %(tsk, ev))['Start Date'].min())
    sampleDict[ev] = Sample(ev, df.Tasks.unique().tolist(), dur)
N = 2
ind = np.arange(N)

stacker = 0
for idx, ev in enumerate(df.Sample.unique()):
    r = [int(t.seconds/60) for t in sampleDict[ev].duration]
    if idx ==0:
        plt.bar(ind, r)
        stacker = r
    else:
        plt.bar(ind, r, bottom=stacker)
        stacker = r
plt.xticks(ind, sampleDict[ev].tasks)
plt.legend(df.Sample.unique())
plt.show()

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sample.xlsx

Excellent,