I have created this plot where I have "observed E. coli" on the the left side "y axis", "modelled E. coli" on the right side "y axis" and "dates" on the "x axis".

The code is this

# -*- coding: utf-8 -*- 
import numpy as np
import matplotlib.pyplot as plt
import pandas as pd

source = "Sample_table.csv"
df = pd.read_csv(source, encoding = 'unicode_escape')

x = df['Date_1']
y1 = df['Obs_Ec']
y2 = df['Rain']
y3 = df['Mod_Ec']

# Plot Line1 (Left Y Axis)
fig, ax1 = plt.subplots(1,1,figsize=(10,6), dpi= 80)

# Plot Line2 (Right Y Axis)
ax2 = ax1.twinx()  # instantiate a second axes that shares the same x-axis
ax2.plot(x, y2, color='tab:blue', linewidth=2.0)

# Plot Line2 (Right Y Axis)
ax3 = ax1.twinx()  # instantiate a second axes that shares the same x-axis
ax3.scatter(x, y3)

# Control limits of the y Axis
a,b = 0,80000
c,d = 0,80000
e,f = 0,35
ax1.set_ylim(a,b)
ax3.set_ylim(c,d)
ax2.set_ylim(e,f)

# Decorations
# ax1 (left Y axis)
ax1.set_xlabel('Date', fontsize=20)
ax1.set_ylabel('E. coli - cfu ml-1', color='tab:red', fontsize=20)
ax1.tick_params(axis='y',rotation=0, labelcolor='tab:red')
ax1.grid(alpha=.0)
ax1.tick_params(axis='both', labelsize=14)

# Plot the scatter points
ax1.scatter(x, y1,
       color="red",  # Color of the dots
       s=50,         # Size of the dots
       alpha=0.5,     # Alpha of the dots
       linewidths=0.5)  # Size of edge around the dots
ax1.scatter(0**np.arange(5), 0**np.arange(5))
ax1.legend(['Observed E. coli'], loc='right',fontsize=14, bbox_to_anchor=(0.2, -0.20))

ax3.scatter(x, y3,
       color="green",  # Color of the dots
       s=50,         # Size of the dots
       alpha=0.5,     # Alpha of the dots
       linewidths=0.5)  # Size of edge around the dots
ax3.scatter(0**np.arange(5), 0**np.arange(5))
ax3.legend(['Modelled E. coli'], loc='right',fontsize=14, bbox_to_anchor=(0.48, -0.20))

# ax2 (right Y axis)
ax2.set_ylabel("Rainfall - mm", color='tab:blue', fontsize=20)
ax2.tick_params(axis='y', labelcolor='tab:blue')
ax2.tick_params(axis='both', labelsize=15)
ax2.set_xticks(np.arange(1, len(x), 4))
ax2.set_xticklabels(x[0::4], rotation=15, fontdict={'fontsize':10})
ax2.set_title("SP051 - without SR (validation 2018-2020)", fontsize=22)
ax2.legend(['rainfall'], loc='right',fontsize=14, bbox_to_anchor=(1.05, -0.20))
fig.tight_layout()
plt.show()

But this code is giving me this plot below:

I want to change three things in this plot:

1. First, transform the blue line plot into a bars plot.
2. Second, and more important, I want to make the bar plot representing rainfall to be displayed on the top of the plot
3. Third, I need to get rid of the tick marks in black on the right "y axis" by making the "ax3 scatter plot" simply share the "y axis" on the left side.

An example of the plot I want to create is the one below, but instead of the lines I will be using a scatter plot as shown in the previous figure:

Data

The data can be downloaded here: