tuples
tuples are like lists, they have elements which are indexed starting at 0
x = ('ke','is','sleepy')
print(x[2])
y = (1,2,3)
print(y[0])
print(max(y))
Why tuples (an immutable list)?
The immutable list provides a data structure with some integrity and some persistence. It is not possible to accidentally change a tuple.
tuples are immutable!!
- things not to do with tuples:
x = (1,2,3)
x.sort()
x.append()
x.reverse()
# 与list比较可以用的函数
l = list()
t = tuple()
dir(l)
dir(t) # count , index
tuples are more efficient
tuples and assignment
- we can also put a tuple on the left-hand side of an assignment statement
(x,y) = (1, 'ke')
print(y)
(a,b) = (22,33)
print(a)
tuples and dictionaries
d = dict()
d['1'] = 1
d['2'] = 2
for (k,v) in d.items():
print(k,v)
tups = d.items()
print(tups)
tuples are comparable
- if the first item is equal, go to the second item to compare until it finds the element that differs. 只要比较了一个了,后面的就不需要比较
sorting lists of tuples
- first, we sort the dictionary by the key using the items() method and sorted() function.
d = {'a':22, 'h':11, 'f':22}
d.items()
sorted(d.items(),reverse = True)
it's also possible to sort by values instead of key: construct a list of tuples of the form (value, key) we could sort by value.
- sort a tuple by sorted method, then it returns a list. So we need to convert it back to a tuple.
sorted_list = sorted(a_tuple)
new_tuple = tuple(sorted_list)
top10 most common
d = {'a':22, 'h':11, 'f':22}
print(sorted([(v,k) for k,v in d.items()]))
网友评论