How to add title, x axis label and y axis label while using .subplot in matplotlib?

I have a dateframe called for_plot and I am using the following snippet of code to make a bar diagram:

import matlplotlib.pyplot as plt
f, ax = plt.subplots(1,1,figsize=(10,8))
x_1 = for_plot['res_code'] - 0.2
x_2 = for_plot['res_code']
pre = for_plot['n_indnota_pre']
post = for_plot['n_indnota_post']
ax.bar(x_1,pre, width = 0.2, color = 'red')
ax.bar(x_2,post, width = 0.2, color = 'green')
ax.set_xticks([0.9,1.9,2.9])
ax.set_xticklabels(['GEN','ST','SC'])
ax.legend(['pre_nota', 'post_nota'],loc = 1)

ax.xlabel('Constituency Type')
ax.ylabel('No of Independent Candidates')
ax.title('Average No Of Independent Candidates by Constituency Type')

plt.show()

I do understand how to work around with matplotlib but I have a few questions on the nuances:

1. What does f in line 1 of the snippet do? As the snippet stands, what do f and ax represent?
2. I am not able to add the axes labels and chart title (as in the last 4 lines of the snippet) using ax.xlabel('Constituency Type') but while drawing other figures, If I don't call subplot() in the first line and use plt.xlabel('Constituency Type'), it works absolutely fine. Why does it behave this way?

I get the following error:

AttributeError: 'AxesSubplot' object has no attribute 'xlabel'

Edit 1:

f.xlabel('Constituency Type')
f.ylabel('No of Independent Candidates')
f.title('Average No Of Independent Candidates by Constituency Type')

Doesn't work either.

AttributeError:'Figure' object has no attribute 'xlabel'