Adding and removing from lists

Question

I am trying to do a chess game but i have problems and i couldn't find these problems. It is long and hard to read but i am a student and i don't know too much thing in python.

i have a file like that:

move p3 c4

move p4 d3

import sys
f=open(sys.argv[1],'r')
commands=[[line.split()] for line in f.readlines()]
length=len(commands)
counter=0

line8=['R1','N1','B1','QU','KI','B2','N2','R2']
line7=['P1','P2','P3','P4','P5','P6','P7','P8']
line6=[' ',' ',' ',' ',' ',' ',' ',' ']
line5=[' ',' ',' ',' ',' ',' ',' ',' ']
line4=[' ',' ',' ',' ',' ',' ',' ',' ']
line3=[' ',' ',' ',' ',' ',' ',' ',' ']
line2=['p1','p2','p3','p4','p5','p6','p7','p8']
line1=['r1','n1','b1','qu','ki','b2','n2','r2']

for i in range(0,length-1):
    if commands[i][0][0]=='move':
#PAWNS

        if commands[i][0][1] in['p1','p2','p3','p4','p5','p6','p7','p8']:
            letterlist = ['','a','b','c','d','e','f','g','h']
            pawnandnumber=list(commands[i][0][1])
            moveandnumber = list((commands[i][0][2]))
            #LINE BY LINE PAWN MOVES

            if commands[i][0][1] in line2:
                where_is_pawn=line2.index(commands[i][0][1])
                if pawnandnumber[1]==str(letterlist.index(moveandnumber[0])) and (moveandnumber[1]=='3' or '4'):
                    print('>',end=' ')
                    print(commands[i][0])
                    print('OK')
                    if moveandnumber[1]=='3':
                        if line3[where_is_pawn] in ['R1','N1','B1','QU','KI','B2','N2','R2','P1','P2','P3','P4','P5','P6','P7','P8',' ']:
                            line3.pop(where_is_pawn)
                            line2.pop(where_is_pawn)
                            line2.insert(where_is_pawn,' ')
                            line3.insert(where_is_pawn, line2[where_is_pawn])

                    if moveandnumber[1]=='4':
                        if line4[where_is_pawn] in ['R1','N1','B1','QU','KI','B2','N2','R2','P1','P2','P3','P4','P5','P6','P7','P8',' ']:
                            line4.pop(where_is_pawn)
                            line2.pop(where_is_pawn)
                            line2.insert(where_is_pawn, ' ')
                            line4.insert(where_is_pawn, commands[i][0][1])
            if commands[i][0][1] in line3:
                if pawnandnumber[1]==str(letterlist.index(moveandnumber[0])):
                    where_is_pawn = line3.index(commands[i][0][1])
                    if line4[where_is_pawn] in ['R1','N1','B1','QU','KI','B2','N2','R2','P1','P2','P3','P4','P5','P6','P7','P8',' ']:
                        line4.pop(where_is_pawn)
                        line3.pop(where_is_pawn)
                        line3.insert(where_is_pawn, ' ')
                        line4.insert(where_is_pawn, commands[i][0][1])
            if commands[i][0][1] in line4:
                if pawnandnumber[1]==str(letterlist.index(moveandnumber[0])):
                    where_is_pawn = line4.index(commands[i][0][1])
                    if line5[where_is_pawn] in ['R1','N1','B1','QU','KI','B2','N2','R2','P1','P2','P3','P4','P5','P6','P7','P8',' ']:
                        line5.pop(where_is_pawn)
                        line4.pop(where_is_pawn)
                        line4.insert(where_is_pawn,' ')
                        line5.insert(where_is_pawn, commands[i][0][1])
            if commands[i][0][1] in line5:
                if pawnandnumber[1]==str(letterlist.index(moveandnumber[0])):
                    where_is_pawn = line5.index(commands[i][0][1])
                    if line6[where_is_pawn] in ['R1','N1','B1','QU','KI','B2','N2','R2','P1','P2','P3','P4','P5','P6','P7','P8',' ']:
                        line6.pop(where_is_pawn)
                        line5.pop(where_is_pawn)
                        line5.insert(where_is_pawn, ' ')
                        line6.insert(where_is_pawn, commands[i][0][1])

            if commands[i][0][1] in line6:
                if pawnandnumber[1]==str(letterlist.index(moveandnumber[0])):
                    where_is_pawn = line6.index(commands[i][0][1])
                    if line7[where_is_pawn] in ['R1','N1','B1','QU','KI','B2','N2','R2','P1','P2','P3','P4','P5','P6','P7','P8',' ']:
                        line7.pop(where_is_pawn)
                        line6.pop(where_is_pawn)
                        line6.insert(where_is_pawn, ' ')
                        line7.insert(where_is_pawn, commands[i][0][1])

            if commands[i][0][1] in line7:
                if pawnandnumber[1]==str(letterlist.index(moveandnumber[0])):
                    where_is_pawn = line7.index(commands[i][0][1])
                    if line8[where_is_pawn] in ['R1','N1','B1','QU','KI','B2','N2','R2','P1','P2','P3','P4','P5','P6','P7','P8',' ']:
                        line8.pop(where_is_pawn)
                        line7.pop(where_is_pawn)
                        line7.insert(where_is_pawn, ' ')
                        line8.insert(where_is_pawn, commands[i][0][1])


print(line8)
print(line7)
print(line6)
print(line5)
print(line4)
print(line3)
print(line2)
print(line1)

i have an output like that:

> ['move', 'p3', 'c3']
OK
['R1', 'N1', 'p3', 'QU', 'KI', 'B2', 'N2', 'R2']
['P1', 'P2', ' ', 'P4', 'P5', 'P6', 'P7', 'P8']
[' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ']
[' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ']
[' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ']
[' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ']
['p1', 'p2', ' ', 'p4', 'p5', 'p6', 'p7', 'p8']
['r1', 'n1', 'b1', 'qu', 'ki', 'b2', 'n2', 'r2']

p3 should be in 2 upper line and p4 should be 1 upper line what can i do? Or if you think my method is wrong is there an easy way to do it? I am designing a chess game the rows are a,b,c... the lines are 1,2,3... i have an input that contains some commands like 'move' i need to read line by line and print them. Thanks in advance.