Replacing repeated numbers with zero

Question

So the idea of the code is to replace 0 in the blist if the same number occurs in mlist.
I know how to solve the problem if the list if of the same length. But because the first list length is smaller than the second list. I don’t know how to code it.

https://code.sololearn.com/cC4noTfg97zJ/?ref=app

Answer 1

You could cycle through both lists with 2 nested fors. This code will check each item in blist 4 times, using each item in mlist:

for i in range(0, len(mlist)): #Cycles through each item in mlist
for j in range(0, len(blist)): #Cycles through each item in blist
#Check the current item in blist against the current item in mlist
#Replace if same

Answer 2

Sorry! Here's the full code:

for i in range(0, len(mlist)):
for j in range(0, len(blist)):
if mlist[i] == blist[j]:
blist[j] = 0

Answer 3

I...don't mean to confuse but this works:

print( [x if x not in mlist else 0 for x in blist ] )

I'm happy to break that down (or let someone else take a shot; it's potentially a good learning tool to break it down)

Answer 4

Ah, I'm using some things ahead of where you are in the Python lessons I think:
* Lists (and using "in") are covered in section 2, just after "while"
* List comprehensions [ x for x in list ] are in section 5 (More Types)
* The construct: "true value" if condition "false value" is the very last section (Pythonicness...)

When you're ready for those sections, this explanation may help.

# iterates every item in blist, returning a new list:
[x for x in blist]

# Normal "if" statement
if x in mlist:
useValue = 0
else:
useValue = x
...

Shorter way in Python (called ternary in other languages)
"use this value if true" if test_condition else "use this value if false"
useValue = x if x in mlist else 0

So pretending that useValue contains the above test, it looks like this to Python:
[useValue for x in mlist]

Hope that helps you / visitors.

Answer 5

@ Kirk. I ran the code and it works. Thanks.
I was taught using while loops. So this is a new one to me.
But thanks tho

Answer 6

Thanks. I’ve read everything and it make sense. Really appreciate it

Answer 7

@Tamra. Am confused. What goes in the for loops. Thanks.