Section 9.9 Lists and strings

A string is a sequence of characters and a list is a sequence of values, but a list of characters is not the same as a string. To convert from a string to a list of characters, you can use list:

Because list is the name of a built-in function, you should avoid using it as a variable name. I also avoid the letter “l” because it looks too much like the number “1”. So that’s why I use “t”.

The list function breaks a string into individual letters. If you want to break a string into words, you can use the split method:

Once you have used split to break the string into a list of words, you can use the index operator (square bracket) to look at a particular word in the list.

You can call split with an optional argument called a delimiter that specifies which characters to use as word boundaries. The following example uses a hyphen as a delimiter:

Activity 9.9.1.

What is printed by the following statements?

myname = "Edgar Allan Poe"
namelist = myname.split()
init = ""
for aname in namelist:
    init = init + aname[0]
print(init)

Poe
Three characters but not the right ones. namelist is the list of names.
EdgarAllanPoe
Too many characters in this case. There should be a single letter from each name.
EAP
Yes, split creates a list of the three names. The for loop iterates through the names and creates a string from the first characters.
William Shakespeare
That does not make any sense.

join is the inverse of split. It takes a list of strings and concatenates the elements. join is a string method, so you have to invoke it on the delimiter and pass the list as a parameter:

In this case the delimiter is a space character, so join puts a space between words. To concatenate strings without spaces, you can use the empty string, “”, as a delimiter.

Activity 9.9.2.

What would print when the following code executes?

mylist = ['Hannah', 'Grace', 'Olivia', 'Ruth']
delimiter = ''
print(delimiter.join(mylist))

HannahGraceOliviaRuth
Because the delimiter is an empty string (not a space) the list would join without spaces.
Hannah Grace Olivia Ruth
The delimiter is an empty string, not a space.
Hannah, Grace, Olivia, Ruth
The delimiter is an empty string, it does not add spaces and commas automatically.
We would get an error
This will print without causing an error.

Activity 9.9.3.

What would print when the following code executes?

input = "Pat,Smith,girl,65 Elm Street,eat"
pieces = input.split(",")
print(pieces[3])

Smith
That’s pieces[1].
girl
That’s pieces[2]
65 Elm Street
The address is at position 3 in the resulting list.
eat
That’s pieces[4]
We would get an error
Why would this cause an error? We can use indices to get the element at an index in a list.

You have attempted of activities on this page.

Prev Top Next