explanation the differences of the below Parity Check Simulation (python 2.7) codes

def ErrorChannel(coded): received=copy.copy(coded) for i in range(len(coded)): rand=random.random() if rand<=0.02: received[i]=1-received[i] return received

VS

def ErrorChannel(coded)

received=copy.copy(coded)

flag=0;

for i in range(len(coded)-1):

rand=random.random()

x=rand

if flag==1:

flag=0

elif (x<=0.1) & (flag==0):

received[i]=1-received[i]

received[i+1]=1-received[i+1] flag=1

return received