Formatting string in python

Question

I want to write to a file in tabular format and following is code I have written till now.

file_out=open("testing_string","w")
file_out.write("{0:<12} {1:<20} {2:<30}\n".format("TUPLE","LOGFILE STATUS","FSDB STATUS"))
file_out.write("{0:12}".format("Check"))
file_out.write("{0:12}".format("_5"))
file_out.close()

Testing_string looks like this.

TUPLE        LOGFILE STATUS       FSDB STATUS                   
Check       _5

Problem is I want _5 to be with check. Please see that I cannot concatenate check with _5 as check is printed first in file then depeding on some logic I fill LOGFILE STATUS FSDB STATUS. If I am unable to fill status then I check if I have to append _5 or not. so due to this I cannot concatenate string. How to then print _5 right next to Check?

Do the calculation before you write it out. You can't write out 'Check ' and then backspace to write out _5. — AChampion
– AChampion, Commented Jul 19, 2017 at 0:53
@AChampion Not true. One can use the '\b' character, which is the ASCII character code 8, literally called "backspace". It's not elegant, but it's possible. — SethMMorton
– SethMMorton, Commented Jul 19, 2017 at 0:56
This will depend... the file will contain Check \b\b\b_5 which may more or may not work. Displaying that file may show the right thing but the file still contains the extra characters, e.g. if you were to read it back in with python, you would have to explicitly deal with \b\b\b. — AChampion
– AChampion, Commented Jul 19, 2017 at 1:09

SethMMorton · Accepted Answer · 2017-07-19 00:59:25Z

2

In a perfect world, you wouldn't do what is given in the below answer. It is hacky and error-prone and really weird. In a perfect world you would figure out how to write out what you want before you actually write to disk. I assume the only reason you are even considering this is that you are maintaining some old and crusty legacy code and cannot do things "the right way".

This is not the most elegant answer, but you can use the backspace character to overwrite something previously written.

with open('test.txt', 'w') as file_out:
    file_out.write("{0:<12} {1:<20} {2:<30}\n".format("TUPLE","LOGFILE STATUS","FSDB STATUS"))
    file_out.write("{0:12}".format("Check"))
    backup_amount = 12 - len("Check")
    file_out.write("\b" * backup_amount)
    file_out.write("{0:12}".format("_5"))

Output:

TUPLE        LOGFILE STATUS       FSDB STATUS                   
Check_5

This only works in this specific case because we are completely overwriting the previously written characters with new characters - the backspace nearly backs up the cursor but does not actually overwrite the previously written data. Observe:

with open('test.txt', 'w') as f:
    f.write('hello')
    f.write('\b\b')
    f.write('p')

Output:

helpo

Since we backspaced two characters but only wrote one, the original second character still exists. You would have to manually write ' ' characters to overwrite these.

Because of this caveat, you will probably have to start messing with the length of the format codes (i.e. '{0:12}' might need to become '{0:5}' or something else) when you add '_5'. It's going to become messy.

edited Jul 19, 2017 at 0:59

answered Jul 19, 2017 at 0:54

SethMMorton

49.5k13 gold badges72 silver badges90 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

AChampion Over a year ago

Just to be clear the file contains Check \b\b\b_5 not Check_5, this may or may not be sufficient. Personally, I would find some other way to do this.

SethMMorton Over a year ago

@AChampion Agreed, which is why I have a paragraph at the top stating that this is a bad idea and the OP should try to do it the right way in the first place.

vahndi · Accepted Answer · 2017-07-19 00:59:52Z

1

The problem is that you are specifying 12 characters for Check. Try this:

file_out=open("testing_string","w")
file_out.write("{0:<12} {1:<20} {2:<30}\n".format("TUPLE","LOGFILE STATUS","FSDB STATUS"))
file_out.write("{0:5}".format("Check"))
file_out.write("{0:7}".format("_5"))
file_out.close()

answered Jul 19, 2017 at 0:59

vahndi

1,0458 silver badges16 bronze badges

Collectives™ on Stack Overflow

Formatting string in python

2 Answers 2

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related