python Flashcards
Tornado
一个异步web服务器
break
用来终止循环语句
continue
跳过当前循环块中的剩余语句
序列
列表、元组和字符串都是序列，序列的两个主要特点是索引操作符和切片操作符。索引操作符让我们可以从序列中抓取一个特定项目。切片操作符让我们能够获取序列的一个切片，即一部分序列
exec
用来执行储存在字符串或文件中的Python语句。例如
> > > exec ‘print “Hello World”’
Hello World
eval
用来计算存储在字符串中的有效Python表达式。例如
> > > eval(‘2*3’)
6
文档字符串
通常被简称为 docstrings。
在函数的第一个逻辑行的字符串是这个函数的 文档字符串
DocStrings也适用于模块和类。
文档字符串的惯例是一个多行字符串，它的首行以大写字母开始，句号结尾。第二行是空行，从第三行开始是详细的描述。
abs(x)
Return the absolute value of a number. The argument may be a plain or long integer or a floating point number. If the argument is a complex number, its magnitude is returned.
all(iterable)
Return True if all elements of the iterable are true (or if the iterable is empty). Equivalent to:
def all(iterable):
for element in iterable:
if not element:
return False
return True
New in version 2.5.
any(iterable)
Return True if any element of the iterable is true. If the iterable is empty, return False. Equivalent to:
def any(iterable):
for element in iterable:
if element:
return True
return False
New in version 2.5.
basestring
This abstract type is the superclass for str and unicode. It cannot be called or instantiated, but it can be used to test whether an object is an instance of str or unicode. isinstance(obj, basestring) is equivalent to isinstance(obj, (str, unicode)). New in version 2.3.
bin(x)
Convert an integer number to a binary string. The result is a valid Python expression. If x is not a Python int object, it has to define an __index__() method that returns an integer.
bool([x])
Convert a value to a Boolean, using the standard truth testing procedure. If x is false or omitted, this returns False; otherwise it returns True. bool is also a class, which is a subclass of int. Class bool cannot be subclassed further. Its only instances are False and True. If no argument is given, this function returns False.
callable(object)
Return True if the object argument appears callable, False if not. If this returns true, it is still possible that a call fails, but if it is false, calling object will never succeed. Note that classes are callable (calling a class returns a new instance); class instances are callable if they have a __call__() method.
chr(i)
Return a string of one character whose ASCII code is the integer i. For example, chr(97) returns the string ‘a’. This is the inverse of ord(). The argument must be in the range [0..255], inclusive; ValueError will be raised if i is outside that range. See also unichr().
classmethod(function)
Return a class method for function.
A class method receives the class as implicit first argument, just like an instance method receives the instance. The @classmethod form is a function decorator It can be called either on the class (such as C.f()) or on an instance (such as C().f()). The instance is ignored except for its class. If a class method is called for a derived class, the derived class object is passed as the implied first argument.
cmp(x, y)
Compare the two objects x and y and return an integer according to the outcome. The return value is negative if x < y, zero if x == y and strictly positive if x > y.
compile(source, filename, mode[, flags[, dont_inherit]])
Compile the source into a code or AST object. Code objects can be executed by an exec statement or evaluated by a call to eval(). source can either be a string or an AST object. Refer to the ast module documentation for information on how to work with AST objects.
complex([real[, imag]])
Create a complex number with the value real + imag*j or convert a string or number to a complex number. If the first parameter is a string, it will be interpreted as a complex number and the function must be called without a second parameter. The second parameter can never be a string. Each argument may be any numeric type (including complex). If imag is omitted, it defaults to zero and the function serves as a numeric conversion function like int(), long() and float(). If both arguments are omitted, returns 0j.
The complex type is described in Numeric Types — int, float, long, complex.
delattr(object, name)
This is a relative of setattr(). The arguments are an object and a string. The string must be the name of one of the object’s attributes. The function deletes the named attribute, provided the object allows it. For example, delattr(x, ‘foobar’) is equivalent to del x.foobar.
dict([arg])
Create a new data dictionary, optionally with items taken from arg.
dir([object])
Without arguments, return the list of names in the current local scope. With an argument, attempt to return a list of valid attributes for that object.
If the object has a method named __dir__(), this method will be called and must return the list of attributes
divmod(a, b)
Take two (non complex) numbers as arguments and return a pair of numbers consisting of their quotient and remainder when using long division. With mixed operand types, the rules for binary arithmetic operators apply. For plain and long integers, the result is the same as (a // b, a % b). For floating point numbers the result is (q, a % b), where q is usually math.floor(a / b) but may be 1 less than that. In any case q * b + a % b is very close to a, if a % b is non-zero it has the same sign as b, and 0 <= abs(a % b) < abs(b).
enumerate(sequence[, start=0])
Return an enumerate object. sequence must be a sequence, an iterator, or some other object which supports iteration.
For example:
»> for i, season in enumerate([‘Spring’, ‘Summer’, ‘Fall’, ‘Winter’]):
eval(expression[, globals[, locals]])
The arguments are a string and optional globals and locals. If provided, globals must be a dictionary. If provided, locals can be any mapping object.
execfile(filename[, globals[, locals]])
This function is similar to the exec statement, but parses a file instead of a string. It is different from the import statement in that it does not use the module administration — it reads the file unconditionally and does not create a new module.
定义import *的范围
如果有定义__all__=[“对象名”]则只导入指定的对象 ，否则全部
file(filename[, mode[, bufsize]])
Constructor function for the file type, described further in section File Objects. The constructor’s arguments are the same as those of the open() built-in function described below.
When opening a file, it’s preferable to use open() instead of invoking this constructor directly. file is more suited to type testing (for example, writing isinstance(f, file)).
filter(function, iterable)
Construct a list from those elements of iterable for which function returns true. iterable may be either a sequence, a container which supports iteration, or an iterator. If iterable is a string or a tuple, the result also has that type; otherwise it is always a list. If function is None, the identity function is assumed, that is, all elements of iterable that are false are removed.
float([x])
Convert a string or a number to floating point.
format(value[, format_spec])
Convert a value to a “formatted” representation, as controlled by format_spec. Note format(value, format_spec) merely calls value.\_\_format\_\_(format_spec).
frozenset([iterable])
Return a frozenset object, optionally with elements taken from iterable. The frozenset type is described in Set Types — set, frozenset.
getattr(object, name[, default])
Return the value of the named attributed of object.
