Remove last chars when using "while"

Question

I wrote a function in Python to sort my data into a dictionary syntax, but because I'm using while, there is a comma that I would like to remove to avoid having an invalid syntax.

For example with the following code:

file = open("test.txt","w", encoding="utf-8")
number = 0
while number < 5:
    file.write("some text" + ", ")
    number += 1

This will create test.txt with the following text inside:

some text, some text, some text, some text, some text,

I would like to remove the last ", " added by at the end to look like:

some text, some text, some text, some text, some text

Any idea?

One suggestion: construct the entire sentence first (using .join methods if it is a list or something) and write one sentence at a time. essentially, dont use the inner while loop, but instead construct and write a sentence at a time. — Paritosh Singh
– Paritosh Singh, Commented Feb 20, 2019 at 14:22
Remark: The script I actually is longer than the example I wrote above and includes several "if, elif, ...". This is way I'm looking for a simple way to just delete the very last chars of the file. One solution I have is to close() the file, re-open it and using x = x[:-1] to delete the last chars, but I'm sure there is a better way to achieve it. — Skt
– Skt, Commented Feb 20, 2019 at 14:32

blue note · Accepted Answer · 2019-02-20 14:23:08Z

3

I would use join

text_to_write = 5 * ['the text']
file.write(', '.join(text_to_write))

answered Feb 20, 2019 at 14:23

blue note

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Comments

Paritosh Singh · Accepted Answer · 2019-02-20 14:25:21Z

1

Try this:

file = open("test.txt","w", encoding="utf-8")
number = 0
list_to_add = []
while number < 5:
    list_to_add.append("some text") # you can append anything based_on iteration
    number += 1
file.write(','.join(list_to_add))

edited Feb 20, 2019 at 14:25

Paritosh Singh

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answered Feb 20, 2019 at 14:24

Mehrdad Pedramfar

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Comments

NeverMine17 · Accepted Answer · 2019-02-20 14:32:49Z

1

It is possible to do the same thing without while loop:

file = open("test.txt","w", encoding="utf-8")
file.write(", ".join(["some text"] * 5))

", ".join([ ... ]) function joins multiple strings of text in a list using a seperator ,, in your case that equals to:

In [1]: ", ".join(["some text"] * 5)
Out[1]: 'some text, some text, some text, some text, some text'

edited Feb 20, 2019 at 14:32

answered Feb 20, 2019 at 14:27

NeverMine17

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Comments

ohlr · Accepted Answer · 2019-02-20 14:42:57Z

1

simply use a different command for the last element.

file = open("test.txt","w", encoding="utf-8")
number = 0
while number < 5:
    file.write("some text" + ", ")
    if(number == 4):
           file.write("some text") 
    number += 1

edited Feb 20, 2019 at 14:42

answered Feb 20, 2019 at 14:21

ohlr

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2 Comments

Skt Over a year ago

This would work without problem but as my actual "while" loop is much longer than the one above I would have to repeat twice the code.

ohlr Over a year ago

well, you could use an if condition that is active in the last iteration of your algorithm. Below that condition you modify the write command

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