# Summary¶

This chapter introduced a lot of new ideas. The following summary may prove helpful in remembering what you learned.

indexing ([])
Access a single character in a string using its position (starting from 0), or a single item from a list. Example: 'This'[2] evaluates to 'i'. Example: [10, 20, 'hello'][1] evaluates to 20
length function (len)
Returns the number of characters in a string or a list. Example: len('happy') evaluates to 5. Example: len([10, 20 'hello']) evaluates to 3
slicing ([:])
A slice is a substring of a string or a list. Example: 'bananas and cream'[3:6] evaluates to ana (so does 'bananas and cream'[1:4]). Example: [10, 20, 'hello', 'goodbye'][1:3] evaluates to [20, 'hello']
string comparison (>, <, >=, <=, ==, !=)
The six common comparision operators work with strings, evaluating according to lexigraphical order. Examples: 'apple' < 'banana' evaluates to True. 'Zeta' < 'Appricot' evaluates to False. 'Zebra' <= 'aardvark' evaluates to True because all upper case letters precede lower case letters.
in and not in operator (in, not in)
The in operator tests whether one string is contained inside another string. Examples: 'heck' in "I'll be checking for you." evaluates to True. 'cheese' in "I'll be checking for you." evaluates to False.
collection data type
A data type in which the values are made up of components, or elements, that are themselves values.
dot notation
Use of the dot operator, ., to access methods and attributes of an object.
immutable
A compound data type whose elements can not be assigned new values.
index
A variable or value used to select a member of an ordered collection, such as a character from a string, or an element from a list.
whitespace
Any of the characters that move the cursor without printing visible characters. The constant string.whitespace contains all the white-space characters.
aliases
Multiple variables that contain references to the same object.
clone
To create a new object that has the same value as an existing object. Copying a reference to an object creates an alias but doesn’t clone the object.
delimiter
A character or string used to indicate where a string should be split.
element
One of the values in a list (or other sequence). The bracket operator selects elements of a list.
mutable data type
A data type in which the elements can be modified. All mutable types are compound types. Lists are mutable data types; strings are not.
object
A thing to which a variable can refer.
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