python - Sys.stdout.write not working as expected -

i've got test script iterates through 2 string arrays, , want use sys.stdout.write provide user simple 'progress bar'.

my current script:

import sys time import sleep names  = ['serv1', 'serv2', 'serv3', 'serv4', 'serv5'] states = ['running', 'stopped', 'running', 'running', 'stopped'] terminated=0 passed=0 in range (0, len(names)):     if 'running' in states[i]:         print " [*] stop if running {0} ".format(str(names[i]))         #service_info(action, machine, names[i])         terminated+=1     else:         print " [!] passing on {0} ".format(str(names[i]))         passed+=1     sleep(2)     sys.stdout.write(" [ ] {0}/{1} progress left\r".format(i+1, len(names))) 

the expected output sys.stdout.write keep updating, whilst print statements informing user of action. when run this, time sys.stdout.write shown @ end of script. e.g.

 [*] stop if running serv1  [!] passing on serv2  [*] stop if running serv3  [*] stop if running serv4  [!] passing on serv5  [ ] 5/5 progress left 

how can progress left shown below of prints whilst updating?

you'll need flush buffer; output buffered; kept in memory until amount of data has been collected, improve write performance.

the print statement flushes buffer you, when writing stdout directly, need explicitly flush:

sys.stdout.write(" [ ] {0}/{1} progress left\r".format(i+1, len(names))) sys.stdout.flush() 

next, writing stdout after sleeping; next thing replace line next print statement. write message before sleeping:

for in range (0, len(names)):     if 'running' in states[i]:         print " [*] stop if running {0} ".format(str(names[i]))         #service_info(action, machine, names[i])         terminated+=1     else:         print " [!] passing on {0} ".format(str(names[i]))         passed+=1     sys.stdout.write(" [ ] {0}/{1} progress left\r".format(i+1, len(names)))     sys.stdout.flush()     sleep(2)