Python中10个常用的内置函数
大家好，我是小张
在 3.8 版本中，Python 解释器共有近 69 个内置函数可供使用，有了它们能极大地提高编码效率，
image-20210221235544315
数量虽然不少，但在日常搬砖中只用到其中一部分，根据使用频率和用法，列出来几个本人认为不错的内置函数，结合一些例子介绍给大家
complex()
返回一个形如 a+bj 的复数，传入参数分为三种情况：
-
参数为空时，返回
0j -
参数为字符串时，将字符串表达式解释为复数形式并返回
-
参数为两个整数(a,b)时，返回
a+bj -
参数只有一个整数 a 时，虚部 b 默认为0，函数返回
a+0j
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="" cid="n107" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">>>> complex('1+2j')
(1+2j)
complex()
0j
complex(1,2)
(1+2j)
complex(2)
(2+0j)</pre>
dir()
-
不提供参数时，返回当前本地范围内的名称列表
-
提供一个参数时，返回该对象包含的全部属性
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="" cid="n114" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">>>> class Test:
def first(self):
return 1
def second(self):
return 2
dir(Test)# 提供参数时
['class', 'delattr', 'dict', 'dir', 'doc', 'eq', 'format', 'ge', 'getattribute', 'gt', 'hash', 'init', 'init_subclass', 'le', 'lt', 'module', 'ne', 'new', 'reduce', 'reduce_ex', 'repr', 'setattr', 'sizeof', 'str', 'subclasshook', 'weakref', 'first', 'second']
dir()# 未提供参数时
['Test', 'annotations', 'builtins', 'doc', 'loader', 'name', 'package', 'spec']</pre>
divmod(a,b)
-
a -- 代表被除数，整数或浮点数；
-
b -- 代表除数，整数或浮点数；
根据 除法运算 计算 a,b 之间的商和余数，函数返回一个元组(p,q) ，p 代表商 a//b ，q 代表余数 a%b
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="" cid="n122" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">>>> divmod(21,4)
(5, 1)
divmod(20.1,3)
(6.0, 2.1000000000000014)</pre>
enumerate(iterable,start=0)
-
iterable -- 一个可迭代对象，列表、元组序列等
-
start -- 计数索引值，默认初始为0
该函数返回枚举对象是个迭代器，利用 next() 方法依次返回元素值，每个元素以元组形式存在，包含一个计数元素(起始为 start )和 iterable 中对应的元素值；
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="" cid="n130" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">>>> stu = ['xiao','zhang','li','qian']
enumerate(stu)
<enumerate object at 0x0000025331773F48>
list(enumerate(stu))# 默认start = 0
[(0, 'xiao'), (1, 'zhang'), (2, 'li'), (3, 'qian')]
list(enumerate(stu,start = 1))# 默认start = 1
[(1, 'xiao'), (2, 'zhang'), (3, 'li'), (4, 'qian')]</pre>
eval(expression,globals,locals)
-
expression -- 字符串表达式
-
globals -- 变量作用，全局命名空间，如果提供必须为字典形式；可选参数
-
locals -- 变量作用域，局部命名空间，如果提供可为任何映对象；可选参数
将字符串表达式解析，返回执行结果
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="" cid="n140" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">>>> eval("2+2")
4
eval("2==2")
True</pre>
filter(function,iterable)
-
function -- 提供筛选函数名，返回 true 或 false
-
iterable -- 列表、元组等可迭代对象
函数返回 iterable 中满足 function 为 True 的元素；假设有一个列表，我们只需要其中的一部分元素，这时就可以提前写一个函数再借助 filter 来进行过滤
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="" cid="n148" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">>>> num_list = list(range(20))
num_list
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19]
def mod_three(num):
if(num%3==0):
return True
else:
return False
filter(mod_three,num_list)
<filter object at 0x00000253315A6608>
list(filter(mod_three,num_list))
[0, 3, 6, 9, 12, 15, 18]</pre>
isinstance(object,classinfo)
-
object --表示一个类型的对象，若不是此类型， 函数恒返回 False；
-
calssinfo -- 为一个类型元组或单个类型；
判断对象 object 的类型是否为 classinfo 或 classinfo 中其中一个类型，返回 True 或 False；
调试Python程序时，障碍之一就是初始变量没有定义类型，所以在代码编写或者调试时，isinstance() 函数常被用来判断变量类型，帮助我们了解程序整个逻辑防止出错
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="" cid="n157" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">>>> isinstance(num,str)
False
isinstance(num,int)
#### isinstance(object,classinfo)
* object --表示一个类型的对象，若不是此类型， 函数恒返回 False；
* calssinfo -- 为一个类型元组或单个类型；
判断对象 object 的类型是否为 classinfo 或 classinfo 中其中一个类型，返回 True 或 False；
调试Python程序时，障碍之一就是初始变量没有定义类型，所以在代码编写或者调试时，isinstance() 函数常被用来判断变量类型，帮助我们了解程序整个逻辑防止出错
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="" cid="n157" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">>>> isinstance(num,str)
False
>>> isinstance(num,int)
True</pre>
map(function,iterable,...)
-
function -- 执行函数；
-
iterable -- 可迭代对象；
将 iterable 中的每一个元素放入函数 function 中依次执行，得到与 iteable 元素数量相同的迭代器；
map() 中可迭代对象可以为多个，其中函数 function 中的参数为所有可迭代对象中并行元素，最终得到的迭代器的数量是以提供元素数量最少可迭代对象为基准，当数量最少的可迭代对象所有元素输入完毕后即执行停止
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="" cid="n166" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">>>> def fun_a(a,b):
return a+2*b
num_list1 = [1,2,3,4]
num_list2 = [2,3,4,5]
list(map(fun_a,num_list1,num_list2))
[5, 8, 11, 14]</pre>
input()
函数用于人机交互，读取从输入端输入的一行内容，转化为字符串
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="" cid="n169" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">>>> s = input('input:')
input:小张Pyhon
s
'小张Pyhon'</pre>
zip(*iteables)
- *iterables -- 两个或两个以上可迭代对象
将所有 iterable 对象中元素按参数顺序以逐元素聚合在一起，最终得到一个迭代器，迭代器中每个元素是个n元素元组，n 表示函数中输入 iterable 参数数量
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="" cid="n175" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">>>> num_list1 = [1,2,3,4]
num_list2 = [2,3,1,2]
list(zip(num_list1,num_list2))
[(1, 2), (2, 3), (3, 1), (4, 2)]</pre>
zip() 函数功能等价于
<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="" cid="n177" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">def zip(*iterables):
zip('ABCD', 'xy') --> Ax By
sentinel = object()
iterators = [iter(it) for it in iterables]
while iterators:
result = []
for it in iterators:
elem = next(it, sentinel)
if elem is sentinel:
return
result.append(elem)
yield tuple(result)</pre>
除了上面列举的 10 个之外，还有其它 59 个内置函数，想了解的小伙伴可点击下方原文阅读，对于Python开发者来说掌握这些内置函数非常有用，一方面能提高编码效率，另一方面也能提高代码简洁性；在某一方面功能虽然没有第三方库函数强大，但也不能被小觑。
好了以上就是本篇文章的全部内容了，最后感谢大家阅读，我们下期见~
