How to save all Plotly express graphs created using a for loop in a PDF?

Question

I am trying to save all the charts generated through a for loop in a SINGLE PDF file.

My sample data:

import pandas as pd
import numpy as np
import plotly.io as pio
import plotly.express as px
import plotly.graph_objects as go

np.random.seed(0)
df = pd.DataFrame({'State' : np.repeat(['NY', 'TX', 'FL', 'PA'], 12),
                   'Month' : np.tile(pd.date_range('2023-09-01', '2024-08-01', freq = 'MS'), 4),
                   'Actual' : np.random.randint(1000, 1500, size = 48),
                   'Forecast' : np.random.randint(1000, 1500, size = 48)})

df['Month'] = pd.to_datetime(df['Month'])
df.set_index('Month', inplace = True)

I am able to generate the charts in jupyter notebook using:

for s in df['State'].unique():
    d = df.loc[df['State'] == s, ['Actual', 'Forecast']]
    fig = px.line(d, x = d.index, y = d.columns)
    fig.update_layout(title = 'Actuals vs Forecast for ' + s, template = 'plotly_dark', xaxis_title = 'Month')
    fig.update_xaxes(tickformat = '%Y-%B', dtick = 'M1')
    fig.show()

Can someone please let me know how to get all the charts in a single PDF file?

I tried usingfig_trace and make_subplots approach that uses Graph Object go.Scatter inplace of px.line, but it's not working.

Answer 1

At the core, you need to install Kaleido to save the Plotly Express graphs/plots to images. See here for more about that.

Then you can take the images and make a composite image and save as PDF. I used Pillow but there are other ways spelled out more here.

You didn't say if you wanted single-page or multi-page PDF file. (Both are single files.)

Single page output example here.

Multi-page output example here.

In each the header to each is a link to where you can go to get a MyBinder-served session where those notebooks will work as presented.

Here's the essential code for the single-page example with comments that point out the source for additional code, I believe:

import pandas as pd
import numpy as np
import plotly.io as pio
import plotly.express as px
import plotly.graph_objects as go

np.random.seed(0)
df = pd.DataFrame({'State' : np.repeat(['NY', 'TX', 'FL', 'PA'], 12),
                   'Month' : np.tile(pd.date_range('2023-09-01', '2024-08-01', freq = 'MS'), 4),
                   'Actual' : np.random.randint(1000, 1500, size = 48),
                   'Forecast' : np.random.randint(1000, 1500, size = 48)})

df['Month'] = pd.to_datetime(df['Month'])
df.set_index('Month', inplace = True)
images_made = []
for s in df['State'].unique():
    d = df.loc[df['State'] == s, ['Actual', 'Forecast']]
    fig = px.line(d, x = d.index, y = d.columns)
    fig.update_layout(title = 'Actuals vs Forecast for ' + s, template = 'plotly_dark', xaxis_title = 'Month')
    fig.update_xaxes(tickformat = '%Y-%B', dtick = 'M1')
    image_filename = "img_file_"+str(s)+".png"
    images_made.append(image_filename)
    fig.write_image(image_filename)
    #fig.show()

'''
# make them into PDF using Pillow according to https://stackoverflow.com/a/63436357/8508004
from PIL import Image
composite_image = Image.open(images_made[0]).convert("RGB") #start what will be composite after rest appended
images_to_append = [Image.open(x).convert("RGB") for x in images_made[1:]]
composite_image.save("composite_of_plots.pdf", save_all=True, append_images=images_to_append)
'''
# make them into single page PDF using Pillow based on https://stackoverflow.com/a/59042517/8508004
from PIL import Image
# get images    
#img1 = Image.open('image1.png')
#img2 = Image.open('image2.png')
#img3 = Image.open('image3.png')
#img4 = Image.open('image4.png')
images = [Image.open(x) for x in images_made]

# get width and height
#w1, h1 = img1.size
#w2, h2 = img2.size
#w3, h3 = img3.size
#w4, h4 = img4.size
images_width_height_specs = [(x.size) for x in images]

# to calculate size of new image 
#w = max(w1, w2, w3, w4)
#h = max(h1, h2, h3, h4)
w_each = [x[0] for x in images_width_height_specs]
w = max(w_each)
h_each = [x[1] for x in images_width_height_specs]
h = max(h_each)

# create big empty image with place for images
composite_image = Image.new('RGB', (w, h*4))

# put images on new_image
composite_image.paste(images[0], (0, 0))
for idx,x in enumerate(images):
    composite_image.paste(x, (0, h*idx))
#new_image.paste(img3, (0, h))
#new_image.paste(img4, (w, h))

# save it
composite_image.save('composite_as_image.png')
composite_image.save("composite_of_plots.pdf")