import pandas as pd
import matplotlib.pyplot as plt
df = pd.DataFrame({'i':[1,4,4,4,6,6], 'n':[3,5,1,2,3,4]})

ix = df.index%2 == 0
plt.figure()
# produces expected plot with bars offset from x axis
plt.bar(x=df.loc[ix,'i'], height=df.loc[ix, 'n'], bottom=df.loc[ix, 'i'])
plt.figure()
# produces expected plot
plt.bar(x=df.loc[ix,'i'], height=df.loc[ix, 'n'])

ix = df.index%2 == 1
plt.figure()
# the following fails with `TypeError`
# plt.bar(x=df.loc[ix,'i'], height=df.loc[ix, 'n'], bottom=df.loc[ix, 'i'])

# converting to a list fixes the issue and produces the expected outcome.
# note that casting both x and bottom to list is required to produce expected outcome.
plt.bar(x=list(df.loc[ix,'i']), height=df.loc[ix, 'n'], bottom=list(df.loc[ix, 'i']))

plt.figure()
# produces plot with unexpected bar width
plt.bar(x=df.loc[ix,'i'], height=df.loc[ix, 'n'])

# again, converting to list produces expected outcome
plt.figure()
plt.bar(x=list(df.loc[ix,'i']), height=df.loc[ix, 'n'])