re.sub function

Question

We need to create a number formatting system for a contacts database.
Create a program that will take the phone number as input, and if the number starts with "00", replace them with "+".
The number should be printed after formatting.

this is the question asked, but with my code it will replace all the zeroes in the number with a "+". so how can i make it just to check for the first two caracters of the number?
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import re

num = input()

zero = "00"

new_num = re.sub(zero, "+", num)

print(new_num)
####

Answer 1

You can use the string method startswith() to determine if the string starts with 00. If it does, construct a new string with + and the remaining characters.

Using re without defining regular expression patterns seems a little overpowered to me – it can all be achieved with built-in functions

Answer 2

Jayakrishna🇮🇳 I think that would fail for "1230045" ("123+45") as it will replace 00 even if it isn't in the beginning of the string

Answer 3

In that case, as already know that match() checks at beginning then use that combined with sub() function.

if re.match("00", num) :
print(re.sub(zero, "+", num, 1)

I think, those with basic samples from lesson, may it fail other cases. Not tested. OP should try..

Answer 4

Yes, you are right!
you need the count=1 parameter also!
else it will anyway replace the other two zeroes.

tanks

Answer 5

Ramiz Besic check "00120034" – you will still need the count=1 parameter as suggested by Jayakrishna🇮🇳

Answer 6

thanks for your help.
worked with this one:

import re

num = input()

zero = "00"

if num.startswith(zero):
print(re.sub(zero, "+", num))
else:
print(num)

Answer 7

Use count= 1 as parameter to sub function.

new_num = re.sub(zero, "+",num,1)

Syntax is : sub(pattern, replace, string, count=0, flag=0) have default values for count and flags