you need to insert the values in a list and then get the values out of list as you have integers value in list you need to make it a string before getting the values out of list.
while True:
while True:
try:
last_number = int(input('\nEnter last number :'))
except ValueError:
print("\nPlease enter only number")
else:
break
x,y=0,1
z=[]
while y<last_number:
z.append(y)
x,y=y,x+y
a=str(z)[1:-1]
print(f'''The Fibonacci series of number "{last_number}" is {a}.''')
while True:
Repeat=input("\nDo you want to repeat?\n\nYes or No:")
Repeat=Repeat.lower()
if Repeat not in ["yes","y","no","n"]:
print("\nPlease select correct option")
else:
break
if Repeat in ["yes","y"]:
continue
else:
if Repeat in ["no","n"]:
print("\n-----Thank you for using-----")
input()
break
solved while loop:::iterate line only 1 time,while value iterate when condition satisfied