Print bars one above another in matplotlib

I have tried following script ...

import matplotlib.pyplot as plot
import pandas as pd

data = {"PEOI": [100,129,203,406,92,69,69,51,55,34,371], "PCHOI":[-3,-3,-4,10,37,2,-6,16,7,2,-44], "STKS":[4800,4810,4820,4840,4850,4860,4880,4900,4910,4920,4940], "CCHOI":[50,74,45,617,54,2,35,3,3,10,13], "CEOI":[177,182,67,562,118,135,112,30,32,15,184]}     
df = pd.DataFrame(data);

ax1 = df.plot.bar(x="STKS", y=["CEOI","PEOI"], rot=90, width = 0.9, title ="OPEN INTEREST BUILDUP", figsize=(10, 6), fontsize=20)
ax1.set_xlabel("STRIKES", fontweight ='bold', fontsize=25)

ax1.set_ylabel("CHANGE IN OI", fontweight ='bold', fontsize=25)
plot.show(block=True);

Now I have 2 queries...

1- How to make "CEOI"&"PEOI" bars to print one above another(overlapping completely) withe similar gridline as in below image

2- I need two plots at the same time(subplot) for the dataset from my DataFrame....
(a) PEOI, CEOI, STKS
(b) PCHOI, CCHOI, STKS

I don't think you can do what you want using pandas, so we will have to use matplotlib to build this plot from scratch. For the bars being in front of each other, it's just a matter of making two bar plots, giving them the same x values, and plotting them with different widths. For the subplots, I created a list for which data goes to which plot and looped through them, along with the axes, to create the plots. The rest of the code is for formatting (font size and rotation, labels, etc.).

import matplotlib.pyplot as plt
import numpy as np
import pandas as pd

data = {"PEOI": [100, 129, 203, 406, 92, 69, 69, 51, 55, 34, 371],
        "PCHOI": [-3, -3, -4, 10, 37, 2, -6, 16, 7, 2, -44],
        "STKS": [4800, 4810, 4820, 4840, 4850, 4860, 4880, 4900, 4910, 4920, 4940],
        "CCHOI": [50, 74, 45, 617, 54, 2, 35, 3, 3, 10, 13],
        "CEOI": [177, 182, 67, 562, 118, 135, 112, 30, 32, 15, 184]}
df = pd.DataFrame(data)

min_diff_x = np.diff(df.STKS).min()
w1 = 0.8*min_diff_x
w2 = 0.5*min_diff_x

fig, axes = plt.subplots(2, 1, figsize=(10,15))
for (y1, y2), ax in zip([("PEOI", "CEOI"), ("PCHOI", "CCHOI")], axes):
    ax.bar(df["STKS"], df[y1], width=w1, label=y1)
    ax.bar(df["STKS"], df[y2], width=w2, label=y2)
    ax.set_xlabel("STRIKES", fontweight="bold", fontsize=25)
    ax.set_ylabel("CHANGE IN OI", fontweight="bold", fontsize=25)
    ax.tick_params(labelsize=20)
    ax.tick_params(axis="x", rotation=90)
    ax.legend()
    ax.grid()
fig.suptitle("OPEN INTEREST BUILDUP", fontsize=20)
fig.tight_layout()