标签:des os io 使用 ar for 文件 数据 art
>>> s = ‘django is cool‘ >>> words = s.split() >>> words [‘django‘, ‘is‘, ‘cool‘] >>> ‘ ‘.join(words) ‘django is cool‘ >>> s.count(‘o‘) 3 >>> s.find(‘go‘) 4 >>> s.replace(‘django‘, ‘python‘) ‘python is cool‘
一些常用的string函数:
string method | description |
---|---|
count | Number of occurrences of substring in string |
find | Search for substring [also see index, rfind, rindex] |
join | Merge substrings into single delimited string |
replace | Search and replace (sub)string |
split | Split delimited string into substrings [also see splitlines] |
startswith | Does string start with substring [also see endswith] |
strip | Remove leading and trailing whitespace [also see rstrip, lstrip] |
title | Title-case string [also see capitalize, swapcase] |
upper | UPPERCASE string [also see lower] |
isupper | Is string all UPPERCASE? [also see islower, and so forth] |
格式化输出:
>>> ‘%s is number %d‘ % (‘python‘, 1) ‘python is number 1‘ >>> hi = ‘‘‘hello baby‘‘‘ >>> hi ‘hello\nbaby‘ >>> print hi hello baby
tuple里面的元素不能被修改,这与它本身的实现机制有关,在传递参数的时候如果不希望参数被修改也是一种不错的选择。
>>> a = (‘one‘, ‘two‘) >>> a[0] ‘one‘ >>> c = (‘only‘,) >>> c[0] ‘only‘ >>> d = ‘only‘, >>> d[0] ‘only‘
这里需要注意的是声明一个tuple的时候关键是逗号,如果没有下面的例子就只是一个string,注意到这个非常重要,因为很多django的数据类型用的都是tuple:
>>> b = (‘only‘) >>> b[0] ‘o‘
字典是一种有点像哈希表的列表,里面的元素有key和value两个属性。字典的元素可以修改,无序,且大小可以变化。如:
>>> book = {‘title‘:‘django‘, ‘year‘:2008} >>> ‘title‘ in book True >>> book.get(‘pub‘, ‘N/A‘) ‘N/A‘ >>> book[‘pub‘] = ‘Addision‘ >>> book.get(‘pub‘, ‘N/A‘) ‘Addision‘ >>> for key in book: ... print key, ‘:‘, book[key] ... year : 2008 title : django pub : Addision
一些常用函数:
Dictionary Method | Description | |
---|---|---|
keys | Keys (also see iterkeys) | |
values | Values (also see itervalues) | |
items | Key-value pairs (also see iteritems) | |
get | Get value given key else default [also see setdefault, fromkeys] | |
pop | Remove key from dict and return value [also see clear, popitem] | |
update | Update dict with contents of (an)other dict |
>>> data = enumerate((123, ‘abc‘, ‘hello‘)) >>> for i, value in data: ... print i, value ... 0 123 1 abc 2 hello
如尝试打开文件的异常处理:
try: f = open(filename, ‘r‘) except IOError, e: return False, str(e)
也可以把多种错误类型放到一个tuple里面,一次过检测:
try: process_some_data() except (TypeError, ValueError,...), e: print "ERROR ", e
当然也可以对不同类型的异常用不同的处理方法,在最后一种情况通常加上一种Exception,因为这样可以包括所有的异常情况:
try: ... except (TypeError, ValueError), e: ... except ArithmeticError, e: ... except Exception, e: ...
>>> f = open(‘test.txt‘, ‘w‘) >>> f.write(‘foo\n‘) >>> f.write(‘bar\n‘) >>> f.close() >>> f = open(‘test.txt‘, ‘r‘) >>> for line in f: ... print line.rstrip() ... foo bar >>> f.close()
匿名函数使用关键字lambda
,由一个表达式组成,代表函数的返回值。通常的使用方式:
lambda args: expression
sorted(list_of_people, key = lambda person: person.last_name) # 等价于 def get_last_name(person): return person.last_name sorted(list_of_people, key = get_last_name)
python里面的*不是C语言里面的指针,作为参数传递时,* 表示一个tuple(list), ** 表示dict
例子如下:
def check_web_server(host, port, path): ...
调用函数的时候一般用法:
check_web_server(‘127.0.0.1‘, 8080, ‘/admin/‘)
如果把参数作为一个tuple或者dict的形式,可以通过下标的形式传递参数,但是用 * 的方式可以非常方便的完成传参:
host_info = (‘www.python.org‘, 80, ‘/‘) check_web_server(host_info[0],host_info[1], host_info[2]) check_web_server(*host_info) host_info = {‘host‘: ‘www.python.org‘, ‘port‘: 80, ‘path‘: ‘/‘} check_web_server(**host_info)
与其他的一些编程语言不同,python支持类的动态的实例化,如:
>>> class Book(object): ... def __init__(self, name): ... self.name = name ... >>> john = Book(‘John‘) >>> john.father = ‘Jack‘ >>> print john.father Jack
标签:des os io 使用 ar for 文件 数据 art
原文地址:http://www.cnblogs.com/jolin123/p/3961672.html