list=[]
list2=[]
list.append("p")
list.append("&")
list.append("k")
print(list)
operator="&" or "|" or">" or "=" or "~"
prop="p" or "q " or "r"
#a=0
for i in list:
     if i == operator:
 #        a = list.index(i)
  #       print(a - 1)
         nextelem = list[list.index(i) + 1]
         prevelem = list[list.index(i) - 1]
         print(nextelem)
         print(prevelem)
         list.remove(i)
         list2.append(i)
     if nextelem==prop:
           print("voici",nextelem)
           list2.append(nextelem)
           list2.append(prevelem)
print(list2)

Traceback (most recent call last):
  File "C:/Users/PC/PycharmProjects/LIAATP1/TP01.py", line 114, in <module>
    if nextelem==prop:
NameError: name 'nextelem' is not defined