Why Does 'elif' bypass 'if' in my python function

Question

I'm trying to get the expiry date out of string with a function as follows

p = 'Chiet TS Officer ~ ae\nOriginal Registration Date: 1998-06-17 ective Date: 2018-06-20\n\nLatest Revision Date: 2018-05-24 Expiry Date: 2021-06-19\nPage: 1 of 1\n\n \n\n.. making excellence a habit”\n\x0c'
def enddate(p):    
    for line in p.lower().split('\n'):
        if "exp" in line:
            try:
                return(str(dparser.parse(line.split("exp")[-1],fuzzy=True))[0:10])
            except:
                try:
                    return(str(dparser.parse(line),fuzzy=True))[0:10]
                except:
                    return(str(dparser.parse(line.split("20")[-1],fuzzy=True))[0:10])
        elif "20" in line:
            try:
                return(str(dparser.parse(line.split("20")[-1],fuzzy=True))[0:10])
            except:
                return("error")
enddate(p)

'error'

you see that elif bypassed if , if I deleted the elif part it would work well

p = 'Chiet TS Officer ~ ae\nOriginal Registration Date: 1998-06-17 ective Date: 2018-06-20\n\nLatest Revision Date: 2018-05-24 Expiry Date: 2021-06-19\nPage: 1 of 1\n\n \n\n.. making excellence a habit”\n\x0c'
def enddate(p):    
    for line in p.lower().split('\n'):
        if "exp" in line:
            try:
                return(str(dparser.parse(line.split("exp")[-1],fuzzy=True))[0:10])
            except:
                try:
                    return(str(dparser.parse(line),fuzzy=True))[0:10]
                except:
                    return(str(dparser.parse(line.split("20")[-1],fuzzy=True))[0:10])
enddate(p)

'2021-06-19'

so why does that happen? and how can I make my function look for "20" only if all line s don't contain "exp" ?

Answer 1

Simply because "2018" is on the second line, while "expiry" is on the third. So in your case #2, first line nothing happens, second line you enter the elif condition and it returns the error. In case #1, nothing happens until the third line, and then you enter the fist if condition.