17个Python开发技巧

Python 是一门非常实用的语言,其简洁易用令人不得不感概人生苦短。本文罗列了17个非常有用的Python技巧,例如查找、分割和合并列表等。这 17 个技巧都非常简单,但它们都很常用且能激发不一样的思路。

1、变换变量值

"""pythonic way of value swapping"""
a,b=5,10
print(a,b)
a,b=b,a
print(a,b)

2、将列表中的所有元素组合成字符串

a=['python','is','awesome']
print(' '.join(a))

3、查找列表中频率最高的值

"""most frequent element in a list """
a=[1,2,3,1,2,3,2,2,4,5,1]
print(max(set(a),key=a.count))
""" using Counter from collections """
from collections import Counter
cnt=Counter(a)
print(cnt.most_common(3))

4、检查两个字符串是不是由相同字母不同顺序组成

from collections import Counter
Counter(str1)==Counter(str2)

5、反转字符串

"""reversing string with special case of slice step param"""

a='abcdefghijklmnopqrstuvwxyz'
print(a[::-1])

"""iterating over string contents in reverse efficiently."""

for char in reversed(a):
    print(char)

"""reversing an integer through type conversion and slicing."""

num=123456789
print(int(str(num)[::-1]))

6、反转列表

"""reversing list with special case of slice step param"""
a=[5,4,3,2,1]
print(a[::-1])

"""iteration over list contents in reverse efficiently."""
for ele in reversed(a):
    print(ele)

7、转置二维数组

"""transpose 2d array [[a,b],[c,d],[e,f],] -> [[a,c,e],[b,d,f]]"""

original=[['a','b'],['c','d'],['e','f']]
transposed=zip(*original)
print(list(transposed))

8、链式比较

"""chained comparison with all kind of operators"""
b=6
print(4<b<7)
print(1==b<20)

9、链式函数调用

"""calling different functions with same arguments based on condition"""

def product(a,b):
    return a*b

def add(a,b):
    return a+b

b=True
print((product if b else add)(5,7))

10、复制列表

"""a fast way to make a shallow copy of a list"""

b=a
b[0]=10

"""both a and b will be [10,2,3,4,5]"""

b=a[:]
b[0]=10

"""only b will change to [10,2,3,4,5]"""

"""copy list by typecasting method"""

a=[1,2,3,4,5]
print(list(a))

"""using the list.copy() method (python3 only)"""

a=[1,2,3,4,5]
print(a.copy())

"""copy nested lists using copy.deepcopy"""

from copy import deepcopy
l=[[1,2],[3,4]]
l2=deepcopy(l)
print(l2)

11、字典 get 方法

"""returning None or default value, when key is not in dict"""

d={'a':1,'b':2}
print(d.get('c',3));

12、通过“键”排序字典元素

"""sort a dictionary by it's values with the built-in sorted() function and a 'key' argument."""

d={'apple':10,'orange':20,'banana':5,'rotten tomato':1}
print(sorted(d.items(),key=lambda x:x[1]))

"""sort using operator.itemgetter as the sort key instead of a lambda"""

from operator import itemgetter
print(sorted(d.items(),key=itemgetter(1)))

"""sort dict keys by value"""

print(sorted(d,key=d.get))

13、for else

"""else gets called when for loop does not reach break statement"""

a=[1,2,3,4,5]
for el in a:
    if el==0:
        break
else:
    print('did not break out of for loop')

14、转换列表为逗号分割符格式

"""converts list to comma separated string"""

items=['foo','bar','xyz']
print(','.join(items))

"""list of numbers to comma separated"""

numbers=[2,3,5,10]
print(','.join(map(str,numbers)))

"""list of mix data"""

data=[2,'hello',3,3.4]
print(','.join(map(str,data)))

15、合并字典

"""merge dict's"""

d1={'a':1}
d2={'b':2}
#python 3.5
print({**d1,**d2})
print(dict(d1.items() | d2.items()))
d1.update(d2)
print(d1)

16、列表中最小和最大值的索引

"""Find Index of Min/Max Element"""

lst=[40,10,20,30]
def minIndex(lst):
    return min(range(len(lst)),key=list.__getitem__)

def maxIndex(lst):
    return max(range(len(lst)),key=lst.__getitem__)

print(minIndex(lst))
print(maxIndex(lst))

17、移除列表中的重复元素

"""remove duplicate items from list. note: does not preserve the original list order"""

items=[2,2,3,3,1]
newitems2=list(set(items))
print(newitems2)

"""remove dups and keep order"""

from collections import OrderdDict
items=["foo","bar","bar","foo"]
print(list(OrderedDict.fromkeys(items).keys()))