如何使用 python 从文本文件创建二维嵌套列表？答案

【问题标题】：How to create a 2d nested list from a text file using python?如何使用 python 从文本文件创建二维嵌套列表？
【发布时间】：2021-12-28 19:52:00
【问题描述】：

我是一名初级程序员，我正试图弄清楚如何从特定的文本文件创建一个二维嵌套列表（网格）。例如，文本文件如下所示：

文本文件中的前两行将用于创建网格，这意味着它是 3x3。接下来的 9 行将用于填充网格，前 3 行构成第一行，接下来的 3 行构成中间行，最后 3 行构成最后一行。所以嵌套列表看起来像这样：

[[150, 109, 80] [892, 123, 982] [0, 98, 23]]

我该怎么做呢？我能够列出所有内容，但我不知道如何使用前 2 行来定义外部列表中内部列表的大小：

lineContent = []
innerList = ?
     for lines in open('document.txt','r'):
     value = int(lines)
     lineContent.append(value)

从这里开始，我该去哪里使用前 2 行的给定值将其转换为嵌套列表？

提前致谢。

【问题讨论】：

标签： python list nested grid

【解决方案1】：

def parse_txt(filepath):
    lineContent = []
    with open(filepath, 'r') as txt:  # The with statement closes the txt file after its been used
        nrows = int(txt.readline())
        ncols = int(txt.readline())
        for i in range(nrows): # For each row
            row = []
            for j in range(ncols):  # Grab each value in the row
                row.append(int(txt.readline()))
            lineContent.append(row)
    return lineContent

grid_2d = parse_txt('document.txt')

【讨论】：

【解决方案2】：

您可以使用列表推导使这变得非常整洁。

def txt_grid(your_txt):    
    with open(your_txt, 'r') as f:
        # Find columns and rows
        columns = int(f.readline())
        rows = int(f.readline())
        your_list = [[f.readline().strip() for i in range(rows)] for j in range(columns)]
    return your_list

print(txt_grid('document.txt'))

strip() 只是在将每行的换行符 (\n) 存储到列表中之前清除它们。

编辑：修改后的版本，如果您的 txt 文件没有足够的行用于定义的维度。

def txt_grid(your_txt):    
    with open(your_txt, 'r') as f:
        # Find columns and rows
        columns = int(f.readline())
        rows = int(f.readline())
        dimensions = columns * rows

        # Test to see if there are enough rows, creating grid if there are
        nonempty_lines = len([line.strip("\n") for line in f]) # This ignores the first two lines as they have already been written
        if nonempty_lines < dimensions:
            # Either raise an error
            # raise ValueError("Insufficient non-empty rows in text file for given dimensions")
            # Or return something that's not a list
            your_list = None
        else:
            # Creating grid
            your_list = [[f.readline().strip() for i in range(rows)] for j in range(columns)]
    return your_list

print(txt_grid('document.txt'))

【讨论】：

【解决方案3】：

lineContent = []
innerList = []
for lines in open('testQuestion.txt', 'r'):
    value = int(lines)
    lineContent.append(value)

rowSz = lineContent[0]  # row size
colSz = lineContent[1]  # column size
del lineContent[0], lineContent[0]  # makes line contents just the values in the matrix, could also just start currentLine at 2, notice 0 index is repeated because 1st element was deleted 

assert rowSz * colSz == len(lineContent), 'not enough values for array' # to ensure there are enough entries to complete array of rowSz * colSz elements

arr = []
currentLine = 0
for x in range(rowSz):
    arr.append([])
    for y in range(colSz):
        arr[x].append(lineContent[currentLine])
        currentLine += 1

print(arr)

【讨论】：