这里记录Python中容易被忽视的小问题
一、input(...)和raw_input(...)
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#简单的差看帮助文档input(...)和raw_input(...)有如下区别 >>> help(input) Help on built-in function input in module __builtin__: input(...) input([prompt]) -> value Equivalent to eval(raw_input(prompt)). >>> help(raw_input) Help on built-in function raw_input in module __builtin__: raw_input(...) raw_input([prompt]) -> string Read a string from standard input. The trailing newline is stripped. If the user hits EOF (Unix: Ctl-D, Windows: Ctl-Z+Return), raise EOFError. On Unix, GNU readline is used if enabled. The prompt string, if given, is printed without a trailing newline before reading. #可见 input会根据输入的内容eval结果来返回值，即输入纯数字，则得到的就是纯数字 # raw_input返回的才是字符串 #test： >>> a = input("输入数字") 输入数字1>>> type(a) <type 'int'> >>> b=raw_input("输入数字") 输入数字1>>> type(b) <type 'str'> |
ps:在python3.0以后的版本中,raw_input和input合体了,取消raw_input,并用input代替,所以现在的版本input接收的是字符串
二、python三目运算符
虽然Python没有C++的三目运算符(?:)，但也有类似的替代方案，
那就是
1、 true_part if condition else false_part
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>>> 1 if True else 01>>> 1 if False else 00>>> "True" if True else "False"'True'>>> "True" if True else "False"'Falser' |
2、 (condition and [true_part] or [false_part] )[0]
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>>> (True and ["True"] or ["False"])[0] 'True'>>> (False and ["True"] or ["False"])[0] 'False'>>> |
三、获得指定字符串在整个字符串中出现第N次的索引
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# -*- coding: cp936 -*- def findStr(string, subStr, findCnt): listStr = a.split(subStr,findCnt) if len(listStr) <= findCnt: return -1 return len(string)-len(listStr[-1])-len(subStr) #test a = "12345(1)254354(1)3534(1)14"sub = "(1)"N = 2 #查找第2次出现的位置 print findStr(a,sub,N) N = 10 #查找第10次出现的位置 print findStr(a,sub,N) #结果 #>>> #14 #-1 |
四、enumerate用法：
遍历序列的时候，可能同时需要用到序列的索引和对应的值，这时候可以采用enumerate方法进行遍历
enumerate的说明如下：
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>>> help(enumerate) Help on class enumerate in module __builtin__: class enumerate(object) | enumerate(iterable[, start]) -> iterator for index, value of iterable | | Return an enumerate object. iterable must be another object that supports | iteration. The enumerate object yields pairs containing a count (from | start, which defaults to zero) and a value yielded by the iterable argument. | enumerate is useful for obtaining an indexed list: | (0, seq[0]), (1, seq[1]), (2, seq[2]), ... | | Methods defined here: | | __getattribute__(...) | x.__getattribute__('name') <==> x.name | | __iter__(...) | x.__iter__() <==> iter(x) | | next(...) | x.next() -> the next value, or raise StopIteration | | ---------------------------------------------------------------------- | Data and other attributes defined here: | | __new__ = <built-in method __new__ of type object> | T.__new__(S, ...) -> a new object with type S, a subtype of T |
五、遍历序列的方法
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>>> List = ['a','b','c'] >>> for index, value in enumerate(List): print index, value 0 a 1 b 2 c >>> |
六、使用python random模块的sample函数从列表中随机选择一组元素
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importList = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] slice = random.sample(List, 5)#从List中随机获取5个元素，作为一个片断返回 print sliceprint List #原有序列并没有改变。 |
七、用json打印包含中文的列表字典等
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# -*- coding:utf-8 -*- import json #你的列表 listA = [{'path': ['[AWS] \xe7\xbe\x8e\xe5\xb0\x91\xe5\xa5\xb3\xe6\x88\x98\xe5\xa3\xab Sailor Moon Crystal - Moon Pride MV[BIG5][BDrip 1080p x264 AAC][6E5CFE86].mp4'], 'length': 131248608L}, {'path': ['[AWS] \xe7\xbe\x8e\xe5\xb0\x91\xe5\xa5\xb3\xe6\x88\x98\xe5\xa3\xab Sailor Moon Crystal - Moon Pride MV[BIG5][BDrip 720p x264 AAC][639D304A].mp4'], 'length': 103166306L}, {'path': ['[AWS] \xe7\xbe\x8e\xe5\xb0\x91\xe5\xa5\xb3\xe6\x88\x98\xe5\xa3\xab Sailor Moon Crystal - Moon Pride MV[BIG5][BDrip 480p x264 AAC][5A81BACA].mp4'], 'length': 75198408L}]#打印列表print json.dumps(listA, encoding='UTF-8', ensure_ascii=False) |
输出结果：
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>>> [{"path": ["[AWS] 美少女战士 Sailor Moon Crystal - Moon Pride MV[BIG5][BDrip 1080p x264 AAC][6E5CFE86].mp4"], "length": 131248608}, {"path": ["[AWS] 美少女战士 Sailor Moon Crystal - Moon Pride MV[BIG5][BDrip 720p x264 AAC][639D304A].mp4"], "length": 103166306}, {"path": ["[AWS] 美少女战士 Sailor Moon Crystal - Moon Pride MV[BIG5][BDrip 480p x264 AAC][5A81BACA].mp4"], "length": 75198408}] |
希望本文所述对大家的Python程序设计有所帮助。
