Python-12 序列
2017-07-27 15:43
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1、列表、元组、字符串的共同特点
-都可以通过索引得到每一个元素-默认索引值总是从0开始
-可以通过分片的方法得到一个范围内的元素集合
-有很多共同的操作符(重复操作符、拼接操作符、成员关系操作符)
2、序列的常见BIF(内置方法)
-list(iterable)
把一个可迭代的对象转换为列表帮助文档
>>> help(list) Help on class list in module builtins: class list(object) | list() -> new empty list | list(iterable) -> new list initialized from iterable's items | | Methods defined here: | | __add__(self, value, /) | Return self+value. | | __contains__(self, key, /) | Return key in self. | | __delitem__(self, key, /) | Delete self[key]. | | __eq__(self, value, /) | Return self==value. | | __ge__(self, value, /) | Return self>=value. | | __getattribute__(self, name, /) | Return getattr(self, name). | | __getitem__(...) | x.__getitem__(y) <==> x[y] | | __gt__(self, value, /) | Return self>value. | | __iadd__(self, value, /) | Implement self+=value. | | __imul__(self, value, /) | Implement self*=value. | | __init__(self, /, *args, **kwargs) | Initialize self. See help(type(self)) for accurate signature. | | __iter__(self, /) | Implement iter(self). | | __le__(self, value, /) | Return self<=value. | | __len__(self, /) | Return len(self). | | __lt__(self, value, /) | Return self<value. | | __mul__(self, value, /) | Return self*value.n | | __ne__(self, value, /) | Return self!=value. | | __new__(*args, **kwargs) from builtins.type | Create and return a new object. See help(type) for accurate signature. | | __repr__(self, /) | Return repr(self). | | __reversed__(...) | L.__reversed__() -- return a reverse iterator over the list | | __rmul__(self, value, /) | Return self*value. | | __setitem__(self, key, value, /) | Set self[key] to value. | | __sizeof__(...) | L.__sizeof__() -- size of L in memory, in bytes | | append(...) | L.append(object) -> None -- append object to end | | clear(...) | L.clear() -> None -- remove all items from L | | copy(...) | L.copy() -> list -- a shallow copy of L | | count(...) | L.count(value) -> integer -- return number of occurrences of value | | extend(...) | L.extend(iterable) -> None -- extend list by appending elements from the iterable | | index(...) | L.index(value, [start, [stop]]) -> integer -- return first index of value. | Raises ValueError if the value is not present. | | insert(...) | L.insert(index, object) -- insert object before index | | pop(...) | L.pop([index]) -> item -- remove and return item at index (default last). | Raises IndexError if list is empty or index is out of range. | | remove(...) | L.remove(value) -> None -- remove first occurrence of value. | Raises ValueError if the value is not present. | | reverse(...) | L.reverse() -- reverse *IN PLACE* | | sort(...) | L.sort(key=None, reverse=False) -> None -- stable sort *IN PLACE* | | ---------------------------------------------------------------------- | Data and other attributes defined here: | | __hash__ = None >>>
空列表
字符串 迭代成一个列表
>>> a=list() >>> a [] >>> b='beijing' >>> b=list(b) >>> b ['b', 'e', 'i', 'j', 'i', 'n', 'g'] >>>
元组 迭代成一个列表
>>> c = (1,1,2,3,5,8,13,21,34) >>> c = list(c) >>> c [1, 1, 2, 3, 5, 8, 13, 21, 34] >>>
-tuple([iterable])
把一个可迭代对象转换为元组空元组
字符串 ->元组
列表 -> 元组
>>> a = tuple() >>> a () >>> a = 'beijing' >>> a = tuple(a) >>> a ('b', 'e', 'i', 'j', 'i', 'n', 'g') >>> b = ['beijing'] >>> b = tuple(b) >>> b ('beijing',) >>> b[0] 'beijing'
-str(obj)
把obj对象转换为字符串>>> a = (1,1,2,3,5) >>> a = str(a) >>> a '(1, 1, 2, 3, 5)' >>> len(a) 15 >>> num = [1,1,2,3,5,8] >>> sum(num) 20 >>> for i in a: print(i) ( 1 , 1 , 2 , 3 , 5 ) >>>
-len(sub)
返回sub的长度-max()
返回序列或参数集合中的最大值>>> max(1,3,5,2) 5 >>> max([1,4,2,7,3]) #列表 7 >>> max('1,7,2,9,4,6,4') '9' >>> max((1,7,2,9,4,6,4)) #元组 9 >>> >>> b = 'beijing' >>> b = list(b) >>> b ['b', 'e', 'i', 'j', 'i', 'n', 'g'] >>> max(b) 'n' >>> #ascii码
-min()
返回序列或参数集合中的最小值>>> b = 'beijing' >>> b = list(b) >>> b ['b', 'e', 'i', 'j', 'i', 'n', 'g'] >>> min(1,3,5,-2) -2 >>> min([1,4,2,7,-3]) -3 >>> min('1,7,-2,9,4,6,4') ',' >>> min(b) 'b' >>> >>> num = '1234567890' >>> min(num) '0' >>>
-sum(iterable[,start=0])
返回序列iterable和可选参数start的总和>>> num = [1,1,2,3,5,8] >>> sum(num) 20 >>> tuple1 = (1.2,4.5,2.6) >>> sum(tuple1) 8.3 >>> sum(tuple1,1.1) 9.4 >>>
-sorted(iterable,key=None,reverse=False)
返回一个排序的列表,使用方法和列表内置函数(list.sort())一致。>>> b ['b', 'e', 'i', 'j', 'i', 'n', 'g'] >>> sorted(b) ['b', 'e', 'g', 'i', 'i', 'j', 'n'] >>> c = 'beijing' >>> sorted(c) ['b', 'e', 'g', 'i', 'i', 'j', 'n'] >>>
-reversed(sequence)
返回逆向迭代序列的值,和列表内置函数(list.reverse())一致。>>> num [1, 1, 2, 3, 5, 8] >>> reversed(num) <list_reverseiterator object at 0x022BFC50> >>> list(reversed(num)) [8, 5, 3, 2, 1, 1] >>>
-enumerate(iterable)
生成由每个元素的index和item值组成的元组>>> c 'beijing' >>> enumerate(c) <enumerate object at 0x022B2508> >>> tuple(enumerate(c)) ((0, 'b'), (1, 'e'), (2, 'i'), (3, 'j'), (4, 'i'), (5, 'n'), (6, 'g')) >>> >>> list(enumerate(c)) [(0, 'b'), (1, 'e'), (2, 'i'), (3, 'j'), (4, 'i'), (5, 'n'), (6, 'g')] >>>
-zip(iter1 [,iter2 [...]])
返回由各个参数的序列组成的元组>>> d = [1,2,4,5,6] >>> e = [7,8,1,2] >>> zip(d,e) <zip object at 0x022A3788> >>> list(zip(d,e)) [(1, 7), (2, 8), (4, 1), (5, 2)] >>> tuple(zip(d,e)) ((1, 7), (2, 8), (4, 1), (5, 2)) >>>
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