Generate graphs for all the columns in a excel file with Pandas in Google Colab

I'm trying to generate graphs for all the columns from a excel file but I'm having one error. My goal is getting this graphs in png files and then download it. Let me give you some context: I'm reading a csv, for each column, I'm trying to use a for to use .value_counts() and then create a graph once the graph is generated saving this one in a png file with the number of the index my code is this one:

import pandas as pd
from google.colab import files 
from matplotlib import pyplot as plt


df = pd.read_excel('columns.xlsx')

for i in df.columns:
    print(i)
    #i.value_counts().plot(kind="bar", figsize=(15,7), color="#61d199")
    df[i].value_counts().plot(kind="bar", figsize=(15,7), color="#61d199")
    #plt.savefig('viz_movies.png')

Error in this code line:

df[i].value_counts().plot(kind="bar", figsize=(15,7), color="#61d199")

Error:

index 0 is out of bounds for axis 0 with size 0

Also I want to add in the for the names of the files something like this:

for index, number in enumerate(numbers):
    plt.savefig('index.png') #use the index as a name