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pythonlistfor-loop
Alex
Alex

Reputation: 31

Modifying list items in python with for loop and function

I am working through Python: Crash Course and have got to a problem that I am somewhat solving, but there is probably a better way.

I am trying to modify this list:

magicians = ['Houdini', 'Copperfield', 'Blaine']

by adding 'The Great ' before each item in the list to get:

magicians = ['The Great Houdini','The Great Copperfield', 'The great Blaine']

The books says I am supposed to use a for loop and function to do this, and am supposed to directly modify the list. I found an ugly solution, but was hoping there was a better way to solve it. Here is what I came up with.

def make_great(magic):
    """ add 'the great' to a list of magicians"""
    new_magic= []
    for names in magic:
          names = 'the great ' + names 
          new_magic.append(names)

    global magicians
    magicians = new_magic

make_great(magicians)
print(magicians)

Thanks for your help!

Upvotes: 0

Views: 141

Answers (3)

Matt P
Matt P

Reputation: 2347

You have three requirements: 1) Directly modify the original list, 2) Use a function, and 3) Use a for loop. It's a technicality, but unlike the previous answers the following approach does not create a new list first, choosing instead to update each item in the original list itself. So, here's how you can satisfy all of the requirements:

def prefixNames(alist):
    for i,name in enumerate(alist):
        alist[i] = " ".join(("The Great", name))
# example:
magicians = ['Houdini', 'Copperfield', 'Blaine']
prefixNames(magicians)
print(magicians)
['The Great Houdini', 'The Great Copperfield', 'The Great Blaine']

Upvotes: 2

PM 2Ring
PM 2Ring

Reputation: 55479

Here's how to do this modification to the original list using a function and a traditional for loop.

To modify the original list object we can use a slice assignment: magic[:] = new_magic. You should not be trying to modify the global magicians list, you need to work with the magic list object that's passed to the make_great function.

def make_great(magic):
    """ add 'The great ' to a list of magicians"""
    new_magic = []
    for name in magic:
        new_magic.append('The great ' + name)
    magic[:] = new_magic

magicians = ['Houdini', 'Copperfield', 'Blaine'] 
make_great(magicians)
print(magicians)

output

['The great Houdini', 'The great Copperfield', 'The great Blaine']

We can make the function more compact (and slightly more efficient) by using a list comprehension.

def make_great(magic):
    """ add 'The great ' to a list of magicians"""
    magic[:] = ['The great ' + name for name in magic]

Upvotes: 2

Naren Murali
Naren Murali

Reputation: 56886

How about this?

magicians = ['Houdini', 'Copperfield', 'Blaine'] 
print(['The Great ' + x for x in magicians])

Output:

['The Great Houdini', 'The Great Copperfield', 'The Great Blaine']

Upvotes: 1

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