Python 基础知识

1 相关链接 

官网 ： https://www.python.org/

学习网站 ： 

• http://bbs.pythontab.com/forum.php
• http://www.pythontip.com/blog/
• https://www.codecademy.com/learn/python
  
• http://www.tutorialspoint.com/python/

2 基本知识

2.1 数据结构

2.1.1 元组 （）

基本操作： 拼接（+*），切片（基于索引）

t1 = (1,2,3)t2 = ('hi','py')t3 = t1+t2t4 = t1*2print 't3 is:',t3print 't4 is:',t4print 't1[1:]:',t1[1:]

输出 ：

t3 is: (1, 2, 3, 'hi', 'py')t4 is: (1, 2, 3, 1, 2, 3)t1[1:]: (2, 3)

基本函数：x in tup,len(tup),tup.count(),tup.index,cmp(tup1,tup2),max(tup),min(tup),tuple(list)

note: 元组元素不可变

>>> t=(1,2,3)>>> >>> del t[2]Traceback (most recent call last):  File "<pyshell#53>", line 1, in <module>    del t[2]TypeError: 'tuple' object doesn't support item deletion>>> >>> >>> t[2]=4Traceback (most recent call last):  File "<pyshell#56>", line 1, in <module>    t[2]=4TypeError: 'tuple' object does not support item assignment>>> 

2.1.2 列表 []

基本操作：同上

基本函数：cmp(l1,l2),len(l),max(l),min(l),list(l)

                    l.append(x),l.count(x),l.extend(list),l.index(x),l.insert(index,x),l.pop(index),l.remove(x),l.reverse(),l.sort([fun])

Note: 可以通过 dir(list) 查询该类中定义的相关函数，同理对于 元组，用 dir(tuple),字典用 dir(dict)

列表解析：

l=[2+n for n in range(0,5)]l2 = [i for i in l if i>5]print 'l is:',lprint 'l2 is :',l2

输出

l is: [2, 3, 4, 5, 6]l2 is : [6]

2.1.3 字典{}

存储的是键值对

>>> dic = {'a':1,'hi':'a'}>>> dic{'a': 1, 'hi': 'a'}>>> dic['hi']'a'

相关函数 ：cmp(dic1,dic2),len(dic),str(dic),

                     dic.items(),dic.keys(),dic.values(),dic.get(key),dic.pop(key),dic.pop(key),dic.clear(),dic.copy(),dic.fromkeys(s,t),dic.update()

2.1.4 字符串

相关函数

dir(str)
['__add__', '__class__', '__contains__', '__delattr__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__getnewargs__', '__getslice__', '__gt__', '__hash__', '__init__', '__le__', '__len__', '__lt__', '__mod__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__rmod__', '__rmul__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '_formatter_field_name_split', '_formatter_parser', 'capitalize', 'center', 'count', 'decode', 'encode', 'endswith', 'expandtabs', 'find', 'format', 'index', 'isalnum', 'isalpha', 'isdigit', 'islower', 'isspace', 'istitle', 'isupper', 'join', 'ljust', 'lower', 'lstrip', 'partition', 'replace', 'rfind', 'rindex', 'rjust',

 'rpartition', 'rsplit', 'rstrip', 'split', 'splitlines', 'startswith', 'strip', 'swapcase', 'title', 'translate', 'upper', 'zfill']

查该模块相关函数用法：

>>> print(str.format.__doc__)S.format(*args, **kwargs) -> stringReturn a formatted version of S, using substitutions from args and kwargs.The substitutions are identified by braces ('{' and '}').>>> print 'I have {num}{pets}'.format(num=0,pets='dog')I have 0dog>>> 

2.2 流程控制

Python 是用缩进来标识代码块

if/elif/else

for

while

for a in 'hello':    if 'l'==a:        print 'found'        break    print 'letter is :',aprint 'quit'

输出

letter is : hletter is : efoundquit

2.3 函数

import  math def area(d=5):    return d**2 

输出

>>> area()25

2.5 面向对象 

class books:    def __init__(self):        self._writer = 'joy'        self._field  = 'math'        self.__price = 5 #私有变量    def __str__(self):        return 'books(%s,%s)'%(self._writer,self._field)    def __repr__(self):        return str(self)    # 特性装饰器,指出是一个获取函数,不接受除self 以外的参数    @property    def writer(self):        return self._writer    @writer.setter    def writer(self,writer):        self._writer=writer#继承class child_books(books):    def __init__(self):        self._writer = 'jim'        self._field = 'child'    def __repr__(self):        return 'child_books(%s,%s)'%(self._writer,self._field)

输出

>>> b.writer'joy'>>> b.writer='jim'>>> b.writer'jim'>>> c = child_books()>>> cchild_books(jim,child)

2.6 文本文件的读写

import os#逐行读取def print_file1(fname):    f = fopen(fname,'r')    for line in f:        print(line)    fclose()#整个文本文件一起读取def print_file2(fname):    f = fopen(fname,'r')    print f.read()    f.close#写文件def write_file1(fname):    if os.path.isfile('test.txt'):        print 'already exist'    else:        f = fopen('test.txt','w')        f.write('quit,\n')#插入文件到文件开头def insert_title(title,fname):    f = fopen(fname,'r+')    temp = f.read()    temp = title+'\n'+temp    f.seek(0)#文件指针指向文件开头    f.write(temp)

2.7异常处理

 

def get_age():    while True:        try:            n = int(input('how old are u?'))            return 0        except ValueError:            print('please enter an intefer value')        finally:            print('done')