Core Python Programming (2nd Edition)

obj not in seq Tests if obj is not a member of sequence seq
Membership (in, not in)
Membership test operators are used to determine whether an element is in or is a member of a
sequence. For strings, this test is whether a character is in a string, and for lists and tuples, it is whether
an object is an element of those sequences. The in and not in operators are Boolean in nature; they
return true if the membership is confirmed and False otherwise.
The syntax for using the membership operators is as follows:
obj [not] in sequence
Concatenation (+)
This operation allows us to take one sequence and join it with another sequence of the same type. The
syntax for using the concatenation operator is as follows:
sequence1 + sequence2
The resulting expression is a new sequence that contains the combined contents of sequences
sequence1 and sequence2. Note, however, that although this appears to be the simplest way
conceptually to merge the contents of two sequences together, it is not the fastest or most efficient.
For strings, it is less memory-intensive to hold all of the substrings in a list or iterable and use one final
join() string method call to merge them together. Similarly for lists, it is recommend that readers use
the extend() list method instead of concatenating two or more lists together. Concatenation comes in
handy when you need to merge two sequences together on the fly and cannot rely on mutable object
built-in methods that do not have a return value (or more accurately, a return value of None). There is
an example of this case in the section below on slicing.
Repetition ( * )
The repetition operator is useful when consecutive copies of sequence elements are desired. The syntax
for using the repetition operator is as follows:
sequence * copies_int
The number of copies, copies_int, must be an integer (prior to 1.6, long integers were not allowed). As
with the concatenation operator, the object returned is newly allocated to hold the contents of the
multiply replicated objects.
Slices ( [ ], [ : ], [ : : ] )
To put it simply: sequences are data structures that hold objects in an ordered manner. You can get
access to individual elements with an index and pair of brackets, or a consecutive group of elements