find numbers starting certain number with python

Question

i need to find years of dates of births only starting with 18xx and 19xx from string

i'm using regex to solve task

i have testing testbirtdays = 'ABCDEFG 01.19.1701 1801 02.18.1901 2001'

def getNumbers(str): 
    array = re.findall(r'[0-9]+', str) 
    return array 

i can use this function but output will be:

getNumbers(testbirtdays)

#['01', '19', '1701', '1801', '02', '18', '1901', '2001']

my function can't do 2 things:

1. i need numbers only starting wtih 18 and 19

2. i need only 4x numbers to get only years and ignore months/days

so i need output like:

#['1801','1901']

Answer 1

You may use

r'(?<![0-9])1[89][0-9]{2}(?![0-9])'

Or, with word boundaries:

r'\b1[89][0-9]{2}\b'

See the regex demo #1 and regex demo #2 .

Regex details:

• (?<![0-9]) - no ASCII digit allowed immediately on the left
• \\b - a word boundary
• 1 - a 1 digit
• [89] - 8 or 9
• [0-9]{2} - two ASCII digit
• (?![0-9]) - no ASCII digit allowed immediately on the right or
• \\b - a word boundary

See the Python demo :

import re

def getNumbers(s): 
    return re.findall(r'(?<![0-9])1[89][0-9]{2}(?![0-9])', s) 

testbirtdays = 'ABCDEFG 01.19.1701 1801 02.18.1901 2001'
print(getNumbers(testbirtdays)) # => ['1801', '1901']

Answer 2

here is one way :

import re

re.findall(r'\b18\d{2}\b|\b19\d{2}\b', testbirtdays)

output:

['1801', '1901']

Answer 3

You need a more specific regex like 1[8-9][0-9]{2} : a 1 , then one of 89 then 2 digits

You can also do (?:18|19)[0-9]{2} start with 18 or 19 then 2 other digits

def getNumbers(value):
    return re.findall(r'1[8-9][0-9]{2}', value)

r = getNumbers('ABCDEFG 01.19.1701 1801 02.18.1901 2001')
print(r)  # ['1801', '1901']

Answer 4

Try this:

def get_years(str):
    return re.findall(r"((?:18|19)\d{2})\b", str)

print(get_years(testbirtdays))

Output:

['1801', '1901']

Answer 5

test = 'ABCDEFG 01.19.1701 1801 02.18.1901 2001'
pattern = r'1[89]\d{2}'    
re.findall(pattern, test)

The pattern looks for 1 followed by 8 or 9, and 2 more digits.

Output:

['1801', '1901']