Much longer walltime than cpu time when downloading data

[dkobayas-cyber]

I'm using ZTFquery on my JupyterNotebook to download ZTF data. Strangely, the wall time is 5 min 48s, whereas the CPU time is only 1 min 28s. The cell is in idle for 4 minutes, even after the download is done. Does anyone know what is causing this long wall time?

Here is my code:

%matplotlib notebook
from ztfquery import query
import numpy as np
import pandas as pd
from astropy import time

zquery = query.ZTFQuery()

# Input parameters
jdstart, jdend = time.Time("2018-01-01").jd, time.Time("2018-12-01").jd 
fieldid = 710
ccdid = 11

# Create a query
sql_query = (f"field={fieldid}"
             f" and ccdid={ccdid} and filtercode='zg'"
             f" and obsjd BETWEEN {jdstart} AND {jdend}")

# Convert the key information into strings 
root_dir = "/usr/workspace/myusername/data_ZTF/"
str_ccd = 'zg_c'+str(ccdid).zfill(2)

# Directory name
download_dir = root_dir + str_ccd + f'_field%d'%(fieldid) + '_sci/'

# Download data
zquery.download_data(suffix='sciimg.fits', download_dir=download_dir, show_progress=False)

I'm using "%%time" command to show the CPU time and wall time. Here is the result:

CPU times: user 1min 15s, sys: 13.6 s, total: 1min 28s
Wall time: 5min 48s