Having an issue plotting: Columns must be same length as key

Question

I'm new to Python and I'm trying to adjust this code to my data:

import random
import pandas as pd
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.dates as mdates
import seaborn as sns

# Create fake data
cols=['DATE','TAVG']
numdays = 92
date_list =  pd.date_range(start='1/1/2022', periods=numdays, freq='D').astype('str').tolist()
tavg_list = [round(random.uniform(-3.33, 3.33), 2) for i in range(numdays)]
df = pd.DataFrame({"DATE": date_list, "TAVG": tavg_list})

# line plot based on moving average
ma_days = 10  # number of days for moving average

# use seaborn styling on plot
sns.set()
sns.set_context("notebook")    # options: paper, notebook, talk, poster
sns.set_style("darkgrid", {"axes.facecolor":"0.9",'font.family':['Roboto']})

# tuple with size of plot (W,H)
pltsize = (10,7)

# plot bars from the dataframe
ax = df.plot(x='DATE', y='TAVG', kind='bar', legend=False, figsize=pltsize,
             color=(df['TAVG'] > 0).map({True:'darkorange', False:'royalblue'}))

# calc moving average and save to df.
df['MA'] = df.rolling(window=ma_days).mean()

# plot line chart on same bar chart
df.plot(ax=ax, x='DATE', y='MA', kind='line', legend=False, figsize=pltsize,
        color='black', lw=1)

# change x-axis labels to only so monthly
ax.xaxis.set_major_locator(mdates.MonthLocator())

plt.show()

I have this dataframe:

DATE    TAVG
0   1955-06-01  NaN
1   1955-06-02  NaN
2   1955-06-03  NaN
3   1955-06-04  NaN
4   1955-06-05  NaN
... ... ...
5805    2020-08-27  2.067854
5806    2020-08-28  3.267854
5807    2020-08-29  3.067854
5808    2020-08-30  1.567854
5809    2020-08-31  4.167854

The name of it is avgsum, I want to construct a graph like this.

I want a line with the 10 years rolling average and the x axis to display only decades.

When I try writing the code, i always get some kind of error. Like this:

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
/tmp/ipykernel_5361/1371129499.py in <module>
     23 
     24 # calc moving average and save to df.
---> 25 avgsum['MA'] = avgsum.rolling(window=ma_days).mean()
     26 
     27 # plot line chart on same bar chart

~/Downloads/enter/lib/python3.9/site-packages/pandas/core/frame.py in __setitem__(self, key, value)
   3643             self._setitem_array(key, value)
   3644         elif isinstance(value, DataFrame):
-> 3645             self._set_item_frame_value(key, value)
   3646         elif (
   3647             is_list_like(value)

~/Downloads/enter/lib/python3.9/site-packages/pandas/core/frame.py in _set_item_frame_value(self, key, value)
   3773             len_cols = 1 if is_scalar(cols) else len(cols)
   3774             if len_cols != len(value.columns):
-> 3775                 raise ValueError("Columns must be same length as key")
   3776 
   3777             # align right-hand-side columns if self.columns

ValueError: Columns must be same length as key

What am I doing wrong? What should I do? Any help would be appreciated.