Python: if that contains a concatenation can't work

i'm working on a project where i'm scaping a web page. i have a problem on the condition bellow :

 j=-1
 for i in p:
    soup_tr = BeautifulSoup(str(i) ,'html.parser')
       # print(soup_tr)
    cons_intitule= soup_tr.find('table',{"class":"table-results"})
    nb=str(j)
    print(nb)
    if(soup_tr.find('span' ,{"id":"ctl0_CONTENU_PAGE_resultSearch_tableauResultSearch_ctl"+str(j)+"_reference"})):
       print("enter if 1 =======================")
       cons_intitule_ref= (soup_tr.find('span',{"id":"ctl0_CONTENU_PAGE_resultSearch_tableauResultSearch_ctl1_reference"})).get_text()
       resultat.append(cons_intitule_ref)
    //other if conditions using j too ...
 j=j+1

can't access the if condition because of the variable j. what i've tested : 1)- I replaced j with a static value (1) and the condition works perfectly. but when i put j in the condition it doens't work ! 2)- also i printed the id of all iteration to check if j increments , and it perfectly does. now i really can't understand why this condition doesn't work Any Help please. Thanks in advance.