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  • python爬虫之Python中的内置函数

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abs()

Return the absolute value of a number. The argument may be an integer or a floating point number. If the argument is a complex number, its magnitude is returned.

注意复数的绝对值:

>>> a = 1 + 1j
>>> abs(a)
1.4142135623730951

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dict()

class dict(object)

创建字典方式一:

| dict() -> new empty dictionary

创建字典方式二:

| dict(mapping) -> new dictionary initialized from a mapping object's

| (key, value) pairs

>>> dict(([1, 2],[3, 4]))
{1: 2, 3: 4}

创建字典方式三:

| dict(iterable) -> new dictionary initialized as if via:

| d = {}

| for k, v in iterable:

| d[k] = v

创建字典方式四:

| dict(**kwargs) -> new dictionary initialized with the name=value pairs

| in the keyword argument list. For example: dict(one=1, two=2)

|

 >>> dict(one=1,two=2)
{'one': 1, 'two': 2}

| Methods defined here:

| 方法一:

| __contains__(self, key, /)

| True if D has a key k, else False.

| 方法二:

| __delitem__(self, key, /)

| Delete self[key].

| 方法三:

| __eq__(self, value, /)

| Return self==value.

| 方法四:

| __ge__(self, value, /)

| Return self>=v

这里是比较运算符

| 方法五:

| __getattribute__(self, name, /)

| Return getattr(self, name).

 

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help()

Invoke the built-in help system. (This function is intended for interactive use.) If no argument is given, the interactive help system starts on the interpreter console. If the argument is a string, then the string is looked up as the name of a module, function, class, method, keyword, or documentation topic, and a help page is printed on the console. If the argument is any other kind of object, a help page on the object is generated.
This function is added to the built-in namespace by the site module.
Changed in version 3.4: Changes to pydoc and inspect mean that the reported signatures for callables are now more comprehensive and consistent.

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min()

min(iterable, *[, default=obj, key=func]) -> value

min(arg1, arg2, *args, *[, key=func]) -> value

With a single iterable argument, return its smallest item. The

default keyword-only argument specifies an object to return if

the provided iterable is empty.

With two or more arguments, return the smallest argument.

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setattr()

setattr(obj, name, value, /)

Sets the named attribute on the given object to the specified value.

setattr(x, 'y', v) is equivalent to ``x.y = v''

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all()

all(iterable, /)

Return True if bool(x) is True for all values x in the iterable.

If the iterable is empty, return True.

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dir()

dir(...)

dir([object]) -> list of strings

If called without an argument, return the names in the current scope.

如果没有参数数将返回当前空间的变量名&方法名

Else, return an alphabetized list of names comprising (some of) the attributes

of the given object, and of attributes reachable from it.

If the object supplies a method named __dir__, it will be used; otherwise

the default dir() logic is used and returns:

for a module object: the module's attributes.

for a class object: its attributes, and recursively the attributes

of its bases.

for any other object: its attributes, its class's attributes, and

recursively the attributes of its class's base classes.

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hex()

hex(number, /)

Return the hexadecimal representation of an integer.

>>> hex(12648430)

'0xc0ffee'

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next()

next(...)

next(iterator[, default])

Return the next item from the iterator. If default is given and the iterator

is exhausted, it is returned instead of raising StopIteration.

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slice()

>>> a = slice(0, 4, 2)

>>> b = [3, 4,2, 3, 4, 2, 3, 2, 4, 4,5,6 ,6]

>>> b[a]

[3, 2]

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any()

any(iterable, /)

Return True if bool(x) is True for any x in the iterable.

If the iterable is empty, return False.

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divmod()

>>> divmod(9, 5)

(1, 4)

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id()

>>> a = 2

>>> b = 2

>>> id(a)

4453115248

>>> id(b)

4453115248

>>> a = [1, 2, 3]

>>> b = [1, 2, 3]

>>> id(a)

4461028744

>>> id(b)

4461057736

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object()

class object

| The most base type

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sorted()

sorted(iterable, /, *, key=None, reverse=False)

Return a new list containing all items from the iterable in ascending order.

这个函数会返回一个新的list,这一点跟sort不同

A custom key function can be supplied to customize the sort order, and the

reverse flag can be set to request the result in descending order.

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ascii()

ascii(obj, /)

Return an ASCII-only representation of an object.

这是嘛意思呢?

>>> ascii(3)

'3'

>>> ascii('a')

"'a'"

As repr(), return a string containing a printable representation of an

object, but escape the non-ASCII characters in the string returned by

repr() using \x, \u or \U escapes. This generates a string similar

to that returned by repr() in Python 2.

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enumerate()

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__(self, name, /)

| Return getattr(self, name).

|

| __iter__(self, /)

| Implement iter(self).

|

| __new__(*args, **kwargs) from builtins.type

| Create and return a new object. See help(type) for accurate signature.

|

| __next__(self, /)

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input()

input()输入的是str类型

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oct()

八进制

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staticmethod()

静态方法

********************************************************************************************

bin()

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eval()

>>> eval("print('hello world')")

hello world

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int()

>>> s = '4.333'

>>> int(eval(s))

4

********************************************************************************************

open()

open(file, mode='r', buffering=-1, encoding=None, errors=None, newline=None, clo

sefd=True, opener=None)

Open file and return a stream. Raise IOError upon failure.

********************************************************************************************

str()

Last login: Tue Jun 12 11:51:19 on ttys000

hujinzhaodeMacBook-Air:~ andy$ python

Python 3.6.4 |Anaconda, Inc.| (default, Jan 16 2018, 12:04:33)

[GCC 4.2.1 Compatible Clang 4.0.1 (tags/RELEASE_401/final)] on darwin

Type "help", "copyright", "credits" or "license" for more information.

>>> a = 3

>>> str(a)

'3'

>>> help(str)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

| S.upper() -> str

|

| Return a copy of S converted to uppercase.

|

| zfill(...)

| S.zfill(width) -> str

|

| Pad a numeric string S with zeros on the left, to fill a field

| of the specified width. The string S is never truncated.

|

| ----------------------------------------------------------------------

| Static methods defined here:

|

| maketrans(x, y=None, z=None, /)

| Return a translation table usable for str.translate().

|

| If there is only one argument, it must be a dictionary mapping Unicode

| ordinals (integers) or characters to Unicode ordinals, strings or None.

| Character keys will be then converted to ordinals.

| If there are two arguments, they must be strings of equal length, and

| in the resulting dictionary, each character in x will be mapped to the

| character at the same position in y. If there is a third argument, it

| must be a string, whose characters will be mapped to None in the result.

********************************************************************************************

bool()

>>> bool()

False

********************************************************************************************

exec()

exec(source, globals=None, locals=None, /)

Execute the given source in the context of globals and locals.

The source may be a string representing one or more Python statements

or a code object as returned by compile().

The globals must be a dictionary and locals can be any mapping,

defaulting to the current globals and locals.

If only globals is given, locals defaults to it.

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isinstance()

>>> class A():

... pass

...

>>> a = A()

>>> isinstance(a, A)

True

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ord()

>>> ord('a')

97

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sum()

********************************************************************************************

bytearray()

>>> help(bytearray)

 

| zfill(...)

| B.zfill(width) -> copy of B

|

| Pad a numeric string B with zeros on the left, to fill a field

| of the specified width. B is never truncated.

|

| ----------------------------------------------------------------------

| Static methods defined here:

|

| maketrans(frm, to, /)

| Return a translation table useable for the bytes or bytearray translate method.

|

| The returned table will be one where each byte in frm is mapped to the byte at

| the same position in to.

|

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