Python|扁平化二维列表的方法

给定一个二维列表，编写一个Python程序将给定的列表转换为扁平列表。

方法#1：使用chain.iterable()

Python3

# Python code to demonstrate
# converting 2d list into 1d list
# using chain.from_iterables
 
# import chain
from itertools import chain
 
ini_list = [[1, 2, 3],
            [3, 6, 7],
            [7, 5, 4]]
             
# printing initial list
print ("initial list ", str(ini_list))
 
# converting 2d list into 1d
# using chain.from_iterables
flatten_list = list(chain.from_iterable(ini_list))
 
# printing flatten_list
print ("final_result", str(flatten_list))

输出：

initial list  [[1, 2, 3], [3, 6, 7], [7, 5, 4]]
final_result [1, 2, 3, 3, 6, 7, 7, 5, 4]

方法 #2：使用列表推导

Python3

# Python code to demonstrate
# converting 2d list into 1d list
# using list comprehension
 
# import chain
from itertools import chain
 
ini_list = [[1, 2, 3],
            [3, 6, 7],
            [7, 5, 4]]
             
# printing initial list
print ("initial list ", str(ini_list))
 
# converting 2d list into 1d
# using list comprehension
flatten_list = [j for sub in ini_list for j in sub]
 
# printing flatten_list
print ("final_result", str(flatten_list))

输出：

initial list  [[1, 2, 3], [3, 6, 7], [7, 5, 4]]
final_result [1, 2, 3, 3, 6, 7, 7, 5, 4]

方法#3：使用 functools.reduce

Python3

# Python code to demonstrate
# converting 2d list into 1d list
# using functools.reduce
 
# import functools
from functools import reduce
 
ini_list = [[1, 2, 3],
            [3, 6, 7],
            [7, 5, 4]]
             
# printing initial list
print ("initial list ", str(ini_list))
 
# converting 2d list into 1d
# using functools.reduce
flatten_list = reduce(lambda z, y :z + y, ini_list)
 
# printing flatten_list
print ("final_result", str(flatten_list))

输出：

initial list  [[1, 2, 3], [3, 6, 7], [7, 5, 4]]
final_result [1, 2, 3, 3, 6, 7, 7, 5, 4]

方法 #4：使用 sum
sum 有一个可选参数： sum(iterable [, start])

Python3

# Python code to demonstrate
# converting 2d list into 1d list
# using sum
 
ini_list = [[1, 2, 3],
            [3, 6, 7],
            [7, 5, 4]]
 
# printing initial list
print ("initial list ", str(ini_list))
 
# converting 2d list into 1d
flatten_list = sum(ini_list, [])
 
# printing flatten_list
print ("final_result", str(flatten_list))
 
# This code is contributed by
# Mayank Chaudhary - chaudhary_19

输出：

initial list  [[1, 2, 3], [3, 6, 7], [7, 5, 4]]
final_result [1, 2, 3, 3, 6, 7, 7, 5, 4]

方法 #5：使用 lambda

Python3

#Python 3 code to flatten nested list
#contributed by S Lakshman Rao - kaapalx
ini_list=[[1, 2, 3],
          [3, 6, 7],
          [7, 5, 4]]
 
#Using lambda
 
flatten_list = lambda y:[x for a in y for x in flatten_list(a)] if type(y) is list else [y]
 
print("Initial list ",ini_list) #printing initial list
 
print("Flattened List ",flatten_list(ini_list)) # printing flattened list

输出：

Initial list  [[1, 2, 3], [3, 6, 7], [7, 5, 4]]
Flattened List  [1, 2, 3, 3, 6, 7, 7, 5, 4]

方法 #6：使用 numpy

Python3

#Python 3 code to flatten nested list
#Contributed by S Lakshman Rao - kaapalx
import numpy
 
ini_list=[[1, 2, 3],
          [3, 6, 7],
          [7 ,5, 4]]
 
print("Initial list ",ini_list) #Printing Initial list
 
print("Flattened List ",list(numpy.concatenate(ini_list).flat))
#Using numpy to flatten list and printing the result

输出：

Initial list  [[1, 2, 3], [3, 6, 7], [7, 5, 4]]
Flattened List  [1, 2, 3, 3, 6, 7, 7, 5, 4]