How to properly generate a variable string pattern in Python

Question

I have managed to code a little snippet in Python which generates a character strip whose length equals the length of another string like so:

title = "This is a string"
concat_str = ""
for i in range (0,len(title)): #len(title) == 16
  concat_str += '-'
# resulting string
print(concat_str) # ----------------

Nevertheless, I wish to know whether this is the most pythonic way to implement this. Thanks a lot.

Note that += on strings in loops is O(n²) and should thus be avoided. Although trivial answers exist for this, the typical transformation would be to make a list and call .append in the loop. Then do a "".join afterwards. — Veedrac
– Veedrac, Commented Mar 9, 2015 at 10:05

Antti Haapala · Accepted Answer · 2015-03-08 18:06:09Z

8

The most pythonic way would be:

concat_str = '-' * len(title)

P.S. You do not need to specify 0 as the start for range: range(len(title)) is more Pythonic.

answered Mar 8, 2015 at 18:06

Antti Haapala

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Comments

Malik Brahimi · Accepted Answer · 2015-03-08 18:12:10Z

1

You can use regex to replace all characters with a dash:

concat_str = re.sub('.', '-', title)

answered Mar 8, 2015 at 18:12

Malik Brahimi

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4 Comments

Jon Clements Over a year ago

You could - but why'd you want to get a regex engine involved in something so simple that can be achieved by Antti's answer that'll be faster and involve less overhead?

Malik Brahimi Over a year ago

@JonClements The beauty of programming is the multitude of solutions, I just wanted to mention another. Otherwise, I would have simply repeated Antii.

Jon Clements Over a year ago

Guess we could throw in concat_str = ''.join('-' for ch in title) then :p

DSM Over a year ago

@MalikBrahimi: the beauty of programming in Python is that there should be one obvious way to do it. #Zen

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