ValueError: unsupported format character '{' (0x7b) at index 40 - Python & CURL

Question

I'm trying to create a program that can analyze the speed of a website in the terminal. I have used the curl module to process the command in Linux shell. But I'm getting the following error.

ValueError: unsupported format character '{' (0x7b) at index 40

import subprocess

def webSpeed():
    website = raw_input("Enter name of the website:  ")
    print(website)
    cmd = "curl -s -w 'Website Response Time for :%{url_effective}\n\nLookup Time:\t\t%{time_namelookup}\nConnect Time:\t\t%{time_connect}\nAppCon Time:\t\t%{time_appconnect}\nRedirect Time:\t\t%{time_redirect}\nPre-transfer Time:\t%{time_pretransfer}\nStart-transfer Time:\t%{time_starttransfer}\n\nTotal Time:\t\t%{time_total}\n' -o /dev/null https://%s" %(webiste)
    print(cmd)
    temp = subprocess.call(cmd, shell="TRUE")
    print(temp)

How can I add curl commands in python if it's using curly braces?

Answer 1

When you do

string % format_values

Then every % in string is treated as formatting place. Python found %{ and was confused - it expected %d for placing integers or %s for placing strings, or something else know to it. But formatting code does not use %{ for any format - thus error. When you want to write % which does not have formatting meaning then you should escape it by another % .

Therefore there are two solutions

1. either change all % (except last %s ) with %%
2. or do not use string % format_values but simply add website to your command since luckily it is at the end

Correct and wrong code examples:

website = "lukaszslusarczyk.pl"
cmd1 = "curl -s -w 'Response Time for %%{url_effective}\t%%{time_connect}\n' -o /dev/null https://%s" % website # OK                                                                                                                  
cmd2 = "curl -s -w 'Response Time for %{url_effective}\t%{time_connect}\n' -o /dev/null https://" + website # OK                                                                                                                      
cmd3 = "curl -s -w 'Response Time for %{url_effective}\t%{time_connect}\n' -o /dev/null https://%s" % website # wrong