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:
Checkpoint 9.9.1.
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.
Checkpoint 9.9.2.
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.
Checkpoint 9.9.3.
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.
