文章目录
- python3函数
- 1内置函数
python3函数
1内置函数
1、abs(numer) 返回数字的绝对值
2、all(iterable) 如果iterable所有的元素都为真值，则返回True
list = [1,2,3,2,3,3]
print(all(list))Truelist2 = [1,2,0,3,3,3]
print(all(list2))False3、any(iterable) 如果iterable所有的元素都为假，则返回False，否则返回True
4、ascii(object) 类似于repr，但是对非ASCII字符进行转义
print(ascii('中文'))
print(ascii('abc'))'\u4e2d\u6587'
'abc'5、bin(integer) 将整数类型转化为以字符串表示的二进制字面量
num = 12345
print(type(num))
strs = bin(num)
print(str)
print(type(strs))<class 'int'>
<class 'str'>
<class 'str'>6、bool(x) 将x转换为bool类型，并返回True或者False
7、bytearray([source,[encoding[,errors]]]) 创建一个bytearray，可以根据指定的字符串给它赋值，还可以指定编码和错误处理方式
返回一个字节数组，字节是4位二进制，
strs= "wangyincan"
print(bytearray(strs,'utf8')) #将字符串转变成字节数组
nums = 2
print(bytearray(nums)) # 传入整数，将返回一个长度为nums大小的字节数组，本例子返回一个长度为2的字节数组bytearray(b'wangyincan')
bytearray(b'\x00\x00')8、bytes([source,[encoding[,errors]]]) 功能和bytearray差不多，返回一个不可修改的bytes对象
strs= "wangyincan"
print(bytes(strs,'utf8'))
nums = 2
print(bytes(nums))
btsA = bytearray(strs,'utf8')
btsA[1]=12 # 这里不会报错
bytesArr = bytes(strs,'utf8')
# bytesArr[1]=12 #这里会报错b'wangyincan'
b'\x00\x00'9、callable(object) 检查对象是否可被调用
10、chr(number) 返回指定数字的Unicode码
print(chr(1))
print(chr(41))
print(chr(122))
print(chr(112)))
z
p11、classmethod(func) 根据实例方法创建一个类方法 （不太明白？？）
12、complex(real[,img]) 返回一个复数
cnum = complex(1,2)
print(cnum)(1+2j)13、delattr(object,name) 删除指定对象的指定属性的值（delete attribute） 需要注意的是，name是string
class people:
name = ''
sex = ''
age = 0
def __init__(self,name,sex,age):
self.name = name
self.sex = sex
self.age = age
p1 = people('wang','man',12)
print(p1.name)
print(hasattr(p1,'name'))
delattr(p1,'name') # 删除属性
print(hasattr(p1,'name'))
print(p1.name) # 发现删除的是属性的值，该属性还在wang
True
True14、dict([mapping-or-sequence]) 创建一个字典，可以根据另一个映射或者(key,value)列表来创建
# 以下创建字典是等价的
a = dict(one=1, two=2, three=3)
b = {'one': 1, 'two': 2, 'three': 3}
c = dict(zip(['one', 'two', 'three'], [1, 2, 3]))
d = dict([('two', 2), ('one', 1), ('three', 3)])
e = dict({'three': 3, 'one': 1, 'two': 2})
a == b == c == d == eTrue15、dir([object]) 列出当前可见作用域中的命令，或列出指定对象（大部分）的属性
import struct
dir() # show the names in the module namespace['In',
'Out',
'_',
'_16',
'__',
'___',
'__builtin__',
'__builtins__',
'__doc__',
'__loader__',
'__name__',
'__package__',
'__spec__',
'_dh',
'_i',
'_i1',
'_i10',
'_i11',
'_i12',
'_i13',
'_i14',
'_i15',
'_i16',
'_i17',
'_i2',
'_i3',
'_i4',
'_i5',
'_i6',
'_i7',
'_i8',
'_i9',
'_ih',
'_ii',
'_iii',
'_oh',
'a',
'b',
'btsA',
'bytesArr',
'c',
'cnum',
'd',
'e',
'exit',
'get_ipython',
'list',
'list2',
'num',
'nums',
'p1',
'people',
'quit',
'strs',
'struct']dir(struct) # show the names in the struct module['Struct',
'__all__',
'__builtins__',
'__cached__',
'__doc__',
'__file__',
'__loader__',
'__name__',
'__package__',
'__spec__',
'_clearcache',
'calcsize',
'error',
'iter_unpack',
'pack',
'pack_into',
'unpack',
'unpack_from']class Shape:
name='w'
def __dir__(self):
return ['area', 'perimeter', 'location'] #从这个例子可以看出，其实dir()的输出内容首先是查看类中的__dir__函数，如果没有自定义将输出所有属性和方法的名称
s = Shape()
dir(s)['area', 'location', 'perimeter']16、divmod(a,b) 返回（a//b, a% b)
# 对于整数
print(divmod(5,2))
# 对于浮点数
print(divmod(5.1,2.0))(2, 1)
(2.0, 1.0999999999999996)17、enumerate(iterable，[start]) 迭代iterable中所有项的(index,item)。start提供开头位置
lista=['a','b','c','d']
for i in enumerate(lista):
print(i)(0, 'a')
(1, 'b')
(2, 'c')
(3, 'd')
[(0, 'a'), (1, 'b'), (2, 'c'), (3, 'd')]18、eval（string[,globals[,locals]]) 计算以字符串表示的表达式，还可以在指定的全局或局部作用域内进行
x = 1
y = eval（'x+1')
print(y)219、filter(function,sequence) 过滤器，返回一个迭代器，用function进行过滤
def isA(x):
if x%2==0:
return True
else:
return False
listA = [1,2,3,4,5,6,7,8,9]
for i in filter(isA,listA):
print(i)
print(filter(isA,listA)) #从这一句可以发现它输出的是一个迭代器，而不是列表2
4
6
8
<filter object at 0x00000210698CC828>20、float(object) 将字符串或数字转化为浮点数
21、format(value[,format_spec]) 返回对指定字符串设置格式后的结果。格式设置规范与字符串方法中的format相同
format_spec的使用，后面再研究
print(format(111)) # 不加format_spec参数，效果和str(value)相同11122、frozenset([iterable]) 创建一个不可修改的集合，这意味着可将其添加到其他集合中去
listF = ['a','a','b',1,1,2,2,3]
fset = frozenset(listF)
print(fset) # 从输出可以看出，它是一个集合
print(set(listF)) #set和frozenset的区别是可改变和不可改变frozenset({1, 2, 3, 'a', 'b'})
{1, 2, 3, 'a', 'b'}23、getattr(object,name[,default]) 返回指定对象中指定属性的值，还可以给这个属性设置默认值。如果没有指定默认值而且，该属性不存在，则返回AttributeError
24、globals() 返回一个表示当前全局作用域的字典
# globals()25、hasattr(object,name) 检查指定对象是否包含指定属性
26、help([object]) 调用内置的帮助系统，或打印有关指定对象的帮助信息
help(set)Help on class set in module builtins:
class set(object)
| set() -> new empty set object
| set(iterable) -> new set object
|
| Build an unordered collection of unique elements.
|
| Methods defined here:
|
| __and__(self, value, /)
| Return self&value.
|
| __contains__(...)
| x.__contains__(y) <==> y in x.
|
| __eq__(self, value, /)
| Return self==value.
|
| __ge__(self, value, /)
| Return self>=value.
|
| __getattribute__(self, name, /)
| Return getattr(self, name).
|
| __gt__(self, value, /)
| Return self>value.
|
| __iand__(self, value, /)
| Return self&=value.
|
| __init__(self, /, *args, **kwargs)
| Initialize self. See help(type(self)) for accurate signature.
|
| __ior__(self, value, /)
| Return self|=value.
|
| __isub__(self, value, /)
| Return self-=value.
|
| __iter__(self, /)
| Implement iter(self).
|
| __ixor__(self, value, /)
| Return self^=value.
|
| __le__(self, value, /)
| Return self<=value.
|
| __len__(self, /)
| Return len(self).
|
| __lt__(self, value, /)
| Return self<value.
|
| __ne__(self, value, /)
| Return self!=value.
|
| __new__(*args, **kwargs) from builtins.type
| Create and return a new object. See help(type) for accurate signature.
|
| __or__(self, value, /)
| Return self|value.
|
| __rand__(self, value, /)
| Return value&self.
|
| __reduce__(...)
| Return state information for pickling.
|
| __repr__(self, /)
| Return repr(self).
|
| __ror__(self, value, /)
| Return value|self.
|
| __rsub__(self, value, /)
| Return value-self.
|
| __rxor__(self, value, /)
| Return value^self.
|
| __sizeof__(...)
| S.__sizeof__() -> size of S in memory, in bytes
|
| __sub__(self, value, /)
| Return self-value.
|
| __xor__(self, value, /)
| Return self^value.
|
| add(...)
| Add an element to a set.
|
| This has no effect if the element is already present.
|
| clear(...)
| Remove all elements from this set.
|
| copy(...)
| Return a shallow copy of a set.
|
| difference(...)
| Return the difference of two or more sets as a new set.
|
| (i.e. all elements that are in this set but not the others.)
|
| difference_update(...)
| Remove all elements of another set from this set.
|
| discard(...)
| Remove an element from a set if it is a member.
|
| If the element is not a member, do nothing.
|
| intersection(...)
| Return the intersection of two sets as a new set.
|
| (i.e. all elements that are in both sets.)
|
| intersection_update(...)
| Update a set with the intersection of itself and another.
|
| isdisjoint(...)
| Return True if two sets have a null intersection.
|
| issubset(...)
| Report whether another set contains this set.
|
| issuperset(...)
| Report whether this set contains another set.
|
| pop(...)
| Remove and return an arbitrary set element.
| Raises KeyError if the set is empty.
|
| remove(...)
| Remove an element from a set; it must be a member.
|
| If the element is not a member, raise a KeyError.
|
| symmetric_difference(...)
| Return the symmetric difference of two sets as a new set.
|
| (i.e. all elements that are in exactly one of the sets.)
|
| symmetric_difference_update(...)
| Update a set with the symmetric difference of itself and another.
|
| union(...)
| Return the union of sets as a new set.
|
| (i.e. all elements that are in either set.)
|
| update(...)
| Update a set with the union of itself and others.
|
| ----------------------------------------------------------------------
| Data and other attributes defined here:
|
| __hash__ = None27、hex(number) 将数字转化为16进制字符串
hex(100)'0x64'28、id(object) 返回指定对象独一无二的id
set1 = {1,2,3}
set2 = {1,2,3}
set3 = set1
print(id(set1))
print(id(set2))
print(id(set3))
# 可以看见set1和set3是同一个id表明它们指向同一个对象2269512314664
2269512314216
226951231466429、input([prompt]) 以字符串的方式返回用户输入的数据，prompt为提升字符串
30、int(object[,radix]) 将字符串或数字转化为整数，还可以指定基数
x = int('100')
y = int('100',10)
z = int('100',16)
w = int('100',2)
print(x)
print(y)
print(z)
print(w)100
100
256
431、isinstance(object,classinfo) 检查object是否是classinfo的实例，其中参数classinfo可以是类对象、类型对象、类和类型对象的元组
class dog:
def __init__(self,name,color):
self.name = name
self.color = color
dog1 = dog
dog2 = dog("dd",'red')
dog3 = dog('dog3','white')
print(isinstance(dog1,dog))
print(isinstance(dog2,dog))
listdog = [dog,dog1]
tupledog = (dog,dog1)
# print(isinstance(dog2,listdog)) #这个会出错
print(isinstance(dog2,tupledog))False
True
True32、issubclass(class1,class2) 检查class1是否是class2的子类（每个类都被视为它自己的子类）
33、iter(object[,sentinel]) 返回一个迭代器对象，即object.iter() 。这个迭代器对象用于迭代序列（如果object支持__getitem__ ）。如果指定了sentinel，这个迭代器将不断调用object，直到返回sentinel。
该方法带sentinel参数时用在文件读取到某一行停止是一个很好的例子
# with open('mydata.txt') as fp:
# for line in iter(fp.readline,''):
# print(line)
# 这个例子是官方文档的，但是不知为何有问题34、len(object) 返回指定对象的长度
35、list([sequence]) 根据指定的序列创建一个列表
lista = list((1,2,3,4))
listb = list({'a':'1','b':'2'})
listc = list({1:'a',2:'b'})
listd = list({'A',1,'B'})
print(lista)
print(listb)
print(listc)
print(listd)[1, 2, 3, 4]
['a', 'b']
[1, 2]
[1, 'A', 'B']36、locals() 返回一个表示当前局部作用域的字典
#locals()37、map(function,sequence,…) 创建一个列表，用序列中的项执行function后返回的值创建
def fd(x):
return x//2
mapa = map(fd,[12,3,45,667]) # python2 中该函数返回list而在python3中返回map对象，是一个可迭代对象
print(type(mapa))
print(list(mapa))<class 'map'>
[6, 1, 22, 333]38、max(object1[,object2,…]) 如果object不是空序列，则返回其中的最大值，否则返回多个object中的最大值
maxRt1 = max([1,2,3,3,4])
maxRt2 = max([1,3],[4,6])
print(maxRt1)
print(maxRt2)4
[4, 6]39、nim(object1[,object2,…]) 作用同max相似
minRt1 = min([1,2,3,3,4])
minRt2 = min([1,3],[4,6])
print(minRt1)
print(minRt2)1
[1, 3]40、next(iterator[,default]) 返回iterator.__next()__的值，还可以指定默认值，默认值是到达了迭代器末尾时将返回的值
listq = iter([1,2,3])
print(next(listq,'end'))
print(next(listq,'end'))
print(next(listq,'end'))
print(next(listq,'end'))
print(next(listq,'end'))1
2
3
end
end
