open input txt open output txt while True and readline strip if not br

a=open("input.txt","r")
b=open('output.txt','w')
S=[]
t = 0
while True and t==0:
    s=a.readline().strip()
    if not s: 
        break
    if s[0]=='+':
        S.append(int(s[1:]))
    if s[0]=='-':
        if len(S)==0:
            b.write('ERROR')
            t = 1
        else:
            S.pop()
        

if t == 0:
    if len(S)==0:
        b.write('EMPTY')
    else:
        
        for i in range (len(S)):
            b.write(str(S[i]))
            b.write(' ')

a.close()
b.close()