I have a python script that queries some systems and then appends the results to a CSV file. This script runs once a week and then emails the CSV file as the last step. However when I open the attachment I get the information on the previous run but not the information from the current run.I can go to the machine running the script and see that the file actually has the current information.
Here are snippets: File Open:
out_exists = os.path.isfile('/depot/sgcap/grid_capacities.csv')
if out_exists:
out = open("/depot/sgcap/grid_capacities.csv","a")
else:
out = open("/depot/sgcap/grid_capacities.csv","a")
out.write(('Date,Site,Installed Capacity (TB),Used Capacity (TB)'))
File write and close:
out.write('\n'+ str(date) + "," + str(s) + ',' + str(xisc_tb) + ',' + str(xusc_tb))
else:
print('\n Errored on http request with status ', response.status_code)
out.close
And lastly the email portion (shamelessly stolen):
#bundle it up and send the email
email = '[email protected]'
password = ''
send_to_email = ['[email protected]','[email protected]']
subject = 'StorageGRID Capacities'
message = 'This morning\'s capacity report'
file_location = ('/depot/sgcap/grid_capacities.csv')
msg = MIMEMultipart()
msg['From'] = email
msg['To'] = ", ".join(send_to_email)
msg['Subject'] = subject
msg.attach(MIMEText(message, 'plain'))
# Setup the attachment
filename = os.path.basename(file_location)
attachment = open(file_location, "rb")
part = MIMEBase('application', 'octet-stream')
part.set_payload(attachment.read())
encoders.encode_base64(part)
part.add_header('Content-Disposition', "attachment; filename= %s" % filename)
# Attach the attachment to the MIMEMultipart object
msg.attach(part)
server = smtplib.SMTP('my.mailserver.com', 25)
#server.starttls()
#server.login(email, password)
text = msg.as_string()
server.sendmail(email, send_to_email, text)
server.quit()
Your writes must be flushed to disk before you send the file. Before that, they are buffered and have NOT been written to the file on disk.
Best practice for flushing is simply to ensure the file handle is closed, as Tanja Bayer notes, either using out.close() or better practice, using a context manager via open ... as.
There are less common cases where you might want to call out.flush() directly but those are a different use case, for long-running processes that need to keep files open for a long time.
Short answer: for normal / small file writes, just close the file handle to write data to disk.
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