Check number of elements fromuser raw_input in a list

Question

I'm fairly new at python and I'm stuck at the following problem, while trying out some ideas: I'd like users to enter 5 ingredients for a cake and store them in a list and give the list back to the user. I tell the user to tell me 5 ingredients. Now I would like python to check if the user really gave me 5 ingredients or otherwise give them an error message. This is what I've got so far.

def recipe():
    #create a list to store the recipe ingredients.
    print "Enter 5 ingredients that could possibly go into a cake: "
    recipeList = []
    ingredients = raw_input("> ")
    recipeList = recipeList.append(ingredients)

    recipeList = [ingredients]

    print recipeList

    if len(ingredients) = 5:
        print "Thanks"
    elif len(ingredients) > 5:
    print "That's too much"
    elif len(ingredients) < 5:
    print "That's too little"
    else:
        print "There's something wrong!"

recipe()

Answer 1

A lot of those lines are redundant. All you need is something like this*:

def recipe():
    """Create a list to store the recipe ingredients."""

    print "Enter 5 ingredients that could possibly go into a cake: "
    ingredients = raw_input("> ").split()
    print ingredients

    if len(ingredients) == 5:
        print "Thanks"
    elif len(ingredients) > 5:
        print "That's too much"
    elif len(ingredients) < 5:
        print "That's too little"
    else:
        print "There's something wrong!"

recipe()

The most important line here is this:

ingredients = raw_input("> ").split()

It basically does two things:

1. Gets the input with raw_input.

2. Splits the input on spaces using str.split. The result will be a list of substrings (the ingredients).

Also, if you are wondering, I made the comment at the top of your function into a proper docstring.

---

*Note: I assumed that the ingredients would be separated by spaces. If however you want to have them separated by something different, such as a comma, then you can give str.split a specific delimiter:

ingredients = raw_input("> ").split(",")

Answer 2

If all your ingredients are one word they will be logically separated by a space so all you would need to do is split the input string on every space. Or you could specify that each ingredient needs to be separated by a comma or some sort of delimiter and split(",")

print "Enter 5 ingredients that could possibly go into a cake: "

    recipeList = raw_input("> ").split(" ")

The equality operator is ==

if len(recipeList ) == 5:

Answer 3

Something line this:

def recipe():
    #create a list to store the recipe ingredients.
    print "Enter 5 ingredients that could possibly go into a cake: "
    recipeList = []
    line = raw_input("> ")         # changed line

    ingredients = line.split()     # changed line, converts the input in an array
                                   # (input separated by spaces)

    recipeList = recipeList.append(ingredients)

    recipeList = [ingredients]

    print recipeList

    if len(ingredients) == 5:      # added the double equal
       print "Thanks"
    elif len(ingredients) > 5:
       print "That's too much"
    elif len(ingredients) < 5:
       print "That's too little"
    else:
       print "There's something wrong!"

recipe()

Answer 4

You'll want to use the split function because raw_input doesn't separate the input by spaces or any other delimiter.

recipeList = ingredients.split()

Also, this comparison should be a double equals, otherwise it's an assignment. Also, it should compare the length of the list, not the user input.

if len(recipeList) == 5: