我想定义一个没有初始化长度的二维数组,如下所示:
Matrix = [][]
但这给出了一个错误:
IndexError:列表索引超出范围
我想定义一个没有初始化长度的二维数组,如下所示:
Matrix = [][]
但这给出了一个错误:
IndexError:列表索引超出范围
当前回答
为便于阅读而重写:
# 2D array/ matrix
# 5 rows, 5 cols
rows_count = 5
cols_count = 5
# create
# creation looks reverse
# create an array of "cols_count" cols, for each of the "rows_count" rows
# all elements are initialized to 0
two_d_array = [[0 for j in range(cols_count)] for i in range(rows_count)]
# index is from 0 to 4
# for both rows & cols
# since 5 rows, 5 cols
# use
two_d_array[0][0] = 1
print two_d_array[0][0] # prints 1 # 1st row, 1st col (top-left element of matrix)
two_d_array[1][0] = 2
print two_d_array[1][0] # prints 2 # 2nd row, 1st col
two_d_array[1][4] = 3
print two_d_array[1][4] # prints 3 # 2nd row, last col
two_d_array[4][4] = 4
print two_d_array[4][4] # prints 4 # last row, last col (right, bottom element of matrix)
其他回答
我在逗号分隔的文件中阅读如下:
data=[]
for l in infile:
l = split(',')
data.append(l)
列表“data”是带有索引数据[row][col]的列表列表
下面是在python中创建矩阵的代码片段:
# get the input rows and cols
rows = int(input("rows : "))
cols = int(input("Cols : "))
# initialize the list
l=[[0]*cols for i in range(rows)]
# fill some random values in it
for i in range(0,rows):
for j in range(0,cols):
l[i][j] = i+j
# print the list
for i in range(0,rows):
print()
for j in range(0,cols):
print(l[i][j],end=" ")
如果我错过了什么,请提出建议。
输入矩阵和打印的用户定义功能
def inmatrix(m,n):
#Start function and pass row and column as parameter
a=[] #create a blank matrix
for i in range(m): #Row input
b=[]#blank list
for j in range(n): # column input
elm=int(input("Enter number in Pocket ["+str(i)+"]["+str(j)+"] ")) #Show Row And column number
b.append(elm) #add value to b list
a.append(b)# Add list to matrix
return a #return Matrix
def Matrix(a): #function for print Matrix
for i in range(len(a)): #row
for j in range(len(a[0])): #column
print(a[i][j],end=" ") #print value with space
print()#print a line After a row print
m=int(input("Enter number of row")) #input row
n=int(input("Enter number of column"))
a=inmatrix(m,n) #call input matrix function
print("Matrix is ... ")
Matrix(a) #print matrix function
在Python中,您将创建一个列表列表。您不必提前声明维度,但可以这样做。例如:
matrix = []
matrix.append([])
matrix.append([])
matrix[0].append(2)
matrix[1].append(3)
现在矩阵[0][0]==2,矩阵[1][0]==3。您还可以使用列表理解语法。本示例使用它两次来构建“二维列表”:
from itertools import count, takewhile
matrix = [[i for i in takewhile(lambda j: j < (k+1) * 10, count(k*10))] for k in range(10)]
如果您需要具有预定义数字的矩阵,可以使用以下代码:
def matrix(rows, cols, start=0):
return [[c + start + r * cols for c in range(cols)] for r in range(rows)]
assert matrix(2, 3, 1) == [[1, 2, 3], [4, 5, 6]]