Plot a chart depending on price and date

Question

I have a problem. I have a dataframe (please see below). That contains prices and dates. I want to show the avg price of every month. How could I do this? I tried that, but I got the following error KeyError: 'month'. How could I plot a chart like below?

   listing_id       date  price  month  year
0           1 2021-09-07  79.00      9  2021
1           2 2021-08-07  80.00      8  2021
2           3 2021-06-07  90.00      6  2021
3           4 2021-06-05  20.00      6  2021

d = {'listing_id': [1, 2, 3, 4],
     'date': ['2021-09-07', '2021-08-07', '2021-06-07', '2021-06-05'],
     'price': ['$79.00', '$80.00', '$90.00', '$20.00']}
df = pd.DataFrame(data=d)
df['price'] = df['price'].str.replace('$', '', regex=False)
df['date'] = pd.to_datetime(df['date'])
df['month'], df['year'] = df.date.dt.month, df.date.dt.year
print(df)

x = df['month'].unique()
y = df.groupby('date').avg()[['price']]

plt.plot(x,y)
plt.show()

KeyError: 'month'

Answer 1

You should convert the price column to a numerical type so that its mean can be calculated, and then perform a groupby month on df.

As @Trenton pointed out, you should make a bar plot instead of a line plot.

df['price'] = df['price'].astype('float')
df.groupby('month')['price'].mean().plot(kind='bar', rot=0)