11. Appendix D: List Operators and Methods

list()

list

Returns a new empty list. You can also use [] to initialize a new empty list

list(sequence)

list

Returns new list initialized from sequence’s items

[ item [,item]+ ]

list

Writing a number of comma-separated items in square brackets constructs a new list of those items

x+y

list

Returns a new list containing the concatenation of the items in x and y

e in x

bool

Returns True if the item e is in x and False otherwise

del x[i]

Deletes the item at index i in x. This is not an expression and does not return a value

x==y

bool

Returns True if x and y contain the same number of items and each of those corresponding items are pairwise equal

x>=y

bool

Returns True if x is greater than or equal to y according to a lexicographical ordering of the elements in x and y. If x and y have different lengths their items are == up to the shortest length, then this returns True if x is longer than y

x<=y

bool

Returns True if x is lexicographically before y or equal to y and False otherwise

x>y

bool

Returns True if x is lexicographically after y and False otherwise

x<y

bool

Returns True if x is lexicographically before y and False otherwise

x!=y

bool

Returns True if x and y are of different length or if some item of x is not == to some item of y. Otherwise it returns False

x[i]

item

Returns the item at index i of x

x[[i]:[j]]

list

Returns the slice of items starting at index i and extending to index j1 in the string. If i is omitted then the slice begins at index 0. If j is omitted then the slice extends to the end of the list. If i is negative then it returns the slice starting at index len(x)i (and likewise for the slice ending at j)

x[i]=e

Assigns the position at index i the value of e in x. The list x must already have an item at index i before this assignment occurs. In other words, assigning an item to a list in this way will not extend the length of the list to accommodate it

x+=y

This mutates the list x to append the items in y

x*=i

This mutates the list x to be i copies of the original x

iter(x)

iterator

Returns an iterator over x

len(x)

int

Returns the number of items in x

x*i

list

Returns a new list with the items of x repeated i times

i*x

list

Returns a new list with the items of x repeated i times

repr(x)

str

Returns a string representation of x

x.append(e)

None

This mutates the value of x to add e as its last element. The function returns None, but the return value is irrelevant since it mutates x

x.count(e)

int

Returns the number of occurrences of e in x by using == equality

x.extend(iter)

None

Mutates x by appending elements from the iterable, iter

x.index(e,[i,[j]])

int

Returns the first index of an element that == e between the the start index, i, and the stop index, j1. It raises ValueError if the value is not present in the specified sequence. If j is omitted then it searches to the end of the list. If i is omitted then it searches from the beginning of the list

x.insert(i, e)

None

Insert e before index i in x, mutating x

x.pop([index])

item

Remove and return the item at index. If index is omitted then the item at len(x)1 is removed. The pop method returns the item and mutates x. It raises IndexError if list is empty or index is out of range

x.remove(e)

None

remove first occurrence of e in x, mutating x. It raises ValueError if the value is not present

x.reverse()

None

Reverses all the items in x, mutating x

x.sort()

None

Sorts all the items of x according to their natural ordering as determined by the item’s _ _cmp_ _ method, mutating x. Two keyword parameters are possible: key and reverse. If reverse True is specified, then the result of sorting will have the list in reverse of the natural ordering. If key f is specified then f must be a function that takes an item of x and returns the value of that item that should be used as the key when sorting