Python REGEX, reformat a string

Question

I'm trying to create a regex that will take a string and replace certain characters

Double or more spaces reduces to one space
The following chars will be replaced by a word: "#" -> "number, "@" -> "at"
Spaces will be replaced with "-", unless its at the end of the string
Contains only a-z, A-Z, 0-9 and: !@#$%&/,
Double or more "-" will reduce to one

"Hello, Wor--ld! 1$2@3-   " -> "hello-wor-ld-1-dollars-2-at-3"

My code:

name = "Hello, World! 1$2@3-   "

name = re.sub("[^a-zA-Z0-9]+","-",name.lower())

print(name)

But it results in "hello-world-1-2-3-"

it becomes lowercase too ? Can you edit example with a # to ensure what it becomes ? — azro
– azro, Commented Jul 4, 2021 at 16:23
Your example doesn't follow your rules at all. What about "dollars" , the comma, the "-" between the elements at the end ... I was ready to answer, but your question is very incomplete regarding your example — azro
– azro, Commented Jul 4, 2021 at 16:25
It seems the !@#$%& should all correspond to some words. What is the full list? "*# -> number, @ -> at, $ -> dollars", and the rest? Please fix your test case. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Jul 4, 2021 at 16:28

Wiktor Stribiżew · Accepted Answer · 2021-07-04 16:34:01Z

1

Here is the code that you may use as a basis to solve your issue:

import re
name = "Hello, World! 1$2@3-   "
name = re.sub("[^a-zA-Z0-9@#$&]+", "-", " ".join(name.lower().split()))
dct = {'#': 'number', '@': 'at', '$': 'dollars', '&': 'and'}
name = re.sub(r'[$@#]', lambda x: f"-{dct[x.group()]}-", name)
print(name.strip('-'))
# => hello-world-1-dollars-2-at-3

See the Python demo.

Notes:

" ".join(name.lower().split()) - removes leading/trailing whitespaces, shrinks multiple whitespaces to a single occurrence between words and splits with whitespace
re.sub("[^a-zA-Z0-9@#$&]+", "-", ...) - replaces all one or more consecutive chars other than alphanumeric, #, @, $ and & chars with a hyphen
re.sub(r'[$@#]', lambda x: f"-{dct[x.group()]}-", name) - replaces specified special chars with words
name.strip('-') removes leading/trailing hyphens.

answered Jul 4, 2021 at 16:34

Wiktor Stribiżew

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5 Comments

Adele Over a year ago

How can I check for a pattern for example when having "$2" the output would be "2-dollars" instead of "dollars-2"? the combination of $ before a number

Adele Over a year ago

When I put for example "Fries for $2" it returns "fries-for2-dollars" instead of "fries-for-2-dollars" or for "Hello, World! 1$2@3- " returns "hello-world-12-dollars-at-3" instead of "hello-world-1-dollars-2-at-3"

Adele Over a year ago

How will I go about making it return for "Fries for $2.99@" -> "fries-for-2-dollars-99-cents-at"?

Adele Over a year ago

If rearranged to: name = re.sub(r'[$@#]', lambda x: f"-{dct[x.group()]}-", name) name = re.sub(r"-*(\$)(\d+)-*", r"\2\1", name) out put would be "hello-world-1-dollars-2-at-3" but "fries-for-dollars-2" instead of "fries-for-2-dollars"

Wiktor Stribiżew Over a year ago

@Adele Please check this Python demo. Your expectations start to diverge, I think 1$2 means 1-2-dollars and not 1-dollars-2. Else, the format is irregular and cannot be solved with regex.

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