Python学习笔记_list&dictionary

list

list.reverse()

list.sort()

list.index(obj):obj is the object to be find out; it returns index of the found object otherwise raise an exception indicating that value does not find.

aList = [123, 'xyz', 'zara', 'abc'];

print "Index for xyz : ", aList.index( 'xyz' ) ; //return  1
print "Index for zara : ", aList.index( 'zara' ) ;//return  2

list.append(x)

list.insert(i, x):insert x after list[i].

list.pop():the last item will be removed.

list.pop(3) :delete the list[3].the argument is index.so sometimes, you may use list.pop(list.index(obj))

list.remove(sth):delete the 'sth'.

list.extend(an_iter):add each item from the iterable an_iter onto the list.

Difference between extend and append:

iteration

warning: we can't modify a list while interating over it.

settle: create another list

dictionary

A dictionary is an unordered collection of key: value pairs, with each key in a dictionary being distinct.

key：immutable

value: mutable

Convert Iterable of Pairs into Dictonary 

dict() 、dict(an_iter)

将一对值转换为dict的key-value形式，前提是key是immutable的。如果一个key值出现了多次，那么这个key对应的value为最后一个key出现时对应的值。如果要转换的值已经是一个dict了，那么就返回一个这个dict的副本。

Get Value in Dictionary by Key

dict[key]、dict.get(key)、dict.get(key, default)

如果key不在这个dictionary里，就返回一个keyError信息；如果提供了default值，那就返回default值。

Remove Key from Dictionary and Return its Value

dict.pop(key)、dict.pop(key, default)

删掉key对应的value，并返回value

Get List of all Key/Value Pairs in Dictionary

dict.items()

返回这个dict中得所有键值对，（key, value）的list形式，经常用于for循环中。