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值得收藏,Python 开发中的高级技巧

更新时间:2020-06-13 03:24:01 作者:startmvc
Python开发中有哪些高级技巧?这是知乎上一个问题,我总结了一些常见的技巧在这里,可能

Python 开发中有哪些高级技巧?这是知乎上一个问题,我总结了一些常见的技巧在这里,可能谈不上多高级,但掌握这些至少可以让你的代码看起来 Pythonic 一点。如果你还在按照类C语言的那套风格来写的话,在 code review 恐怕会要被吐槽了。

列表推导式


>>> chars = [ c for c in 'python' ]
>>> chars
['p', 'y', 't', 'h', 'o', 'n']

字典推导式


>>> dict1 = {'a': 1, 'b': 2, 'c': 3, 'd': 4, 'e': 5}
>>> double_dict1 = {k:v*2 for (k,v) in dict1.items()}
>>> double_dict1
{'a': 2, 'b': 4, 'c': 6, 'd': 8, 'e': 10}

集合推导式


>>> set1 = {1,2,3,4}
>>> double_set = {i*2 for i in set1}
>>> double_set
{8, 2, 4, 6}

合并字典


>>> x = {'a':1,'b':2}
>>> y = {'c':3, 'd':4}
>>> z = {**x, **y}
>>> z
{'a': 1, 'b': 2, 'c': 3, 'd': 4}

复制列表


>>> nums = [1,2,3]
>>> nums[::]
[1, 2, 3]
>>> copy_nums = nums[::]
>>> copy_nums
[1, 2, 3]

反转列表


>>> reverse_nums = nums[::-1]
>>> reverse_nums
[3, 2, 1]
 PACKING / UNPACKING

变量交换


>>> a,b = 1, 2
>>> a ,b = b,a
>>> a
2
>>> b
1

高级拆包


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

或者


>>> a, *b, c = 1,2,3,4,5
>>> a
1
>>> b
[2, 3, 4]
>>> c
5

函数返回多个值(其实是自动packing成元组)然后unpacking赋值给4个变量


>>> def f():
... return 1, 2, 3, 4
...
>>> a, b, c, d = f()
>>> a
1
>>> d
4

列表合并成字符串


>>> " ".join(["I", "Love", "Python"])
'I Love Python'

链式比较


>>> if a > 2 and a < 5:
... pass
...
>>> if 2<a<5:
... pass
yield from
# 没有使用 field from
def dup(n):
 for i in range(n):
 yield i
 yield i
# 使用yield from
def dup(n):
 for i in range(n):
 yield from [i, i]
for i in dup(3):
 print(i)
>>>
0
0
1
1
2
2

in 代替 or


>>> if x == 1 or x == 2 or x == 3:
... pass
...
>>> if x in (1,2,3):
... pass

字典代替多个if else


def fun(x):
 if x == 'a':
 return 1
 elif x == 'b':
 return 2
 else:
 return None
def fun(x):
 return {"a": 1, "b": 2}.get(x)

有下标索引的枚举


>>> for i, e in enumerate(["a","b","c"]):
... print(i, e)
...
0 a
1 b
2 c

生成器

注意区分列表推导式,生成器效率更高


>>> g = (i**2 for i in range(5))
>>> g
<generator object <genexpr> at 0x10881e518>
>>> for i in g:
... print(i)
...
0
1
4
9
16

默认字典 defaultdict


>>> d = dict()
>>> d['nums']
KeyError: 'nums'
>>>
>>> from collections import defaultdict
>>> d = defaultdict(list)
>>> d["nums"]
[]

字符串格式化


>>> lang = 'python'
>>> f'{lang} is most popular language in the world'
'python is most popular language in the world'

列表中出现次数最多的元素


>>> nums = [1,2,3,3]
>>> max(set(nums), key=nums.count)
3

或者


from collections import Counter
>>> Counter(nums).most_common()[0][0]
3

读写文件


>>> with open("test.txt", "w") as f:
... f.writelines("hello")

判断对象类型,可指定多个类型


>>> isinstance(a, (int, str))
True

类似的还有字符串的 startswith,endswith


>>> "http://foofish.net".startswith(('http','https'))
True
>>> "https://foofish.net".startswith(('http','https'))
True
__str__ 与 __repr__ 区别
>>> str(datetime.now())
'2018-11-20 00:31:54.839605'
>>> repr(datetime.now())
'datetime.datetime(2018, 11, 20, 0, 32, 0, 579521)'

前者对人友好,可读性更强,后者对计算机友好,支持 obj == eval(repr(obj))

使用装饰器


def makebold(f):
return lambda: "<b>" + f() + "</b>"
def makeitalic(f):
return lambda: "<i>" + f() + "</i>"
@makebold
@makeitalic
def say():
return "Hello"
>>> say()
<b><i>Hello</i></b>

不使用装饰器,可读性非常差


def say():
return "Hello"
>>> makebold(makeitalic(say))()
<b><i>Hello</i></b>

总结

以上所述是小编给大家介绍的Python 开发中的高级技巧,希望对大家有所帮助,如果大家有任何疑问请给我留言,小编会及时回复大家的。在此也非常感谢大家对脚本之家网站的支持!

python 开发高级技巧 python 技巧