从python中的文件中读取逗号分隔的元组

Question

我试图从一个文件中读取几个由逗号分隔的元组.示例输入文件如下所示:

(0,0),(0,2),(0,4),( - 1,-1),(0,-2),(1,-1),( - 1,-3),

(-1,1),(-1,3),(1,1),(1,3),(1,5),(2,0),(2,2),(3,3),

(2,4),(3,5),(4,4),(5,3),(6,4),(5,5),(7,5)

从这个文件中读取后,我需要一个像这样的元组:

G = ((0, 0), (0, 2), (0, 4), (-1, -1), (0, -2), (1, -1), (-1, -3), \
(-1, 1), (-1, 3), (1, 1), (1, 3), (1, 5), (2, 0), (2, 2), (3, 3), \
(2, 4), (3, 5), (4, 4), (5, 3), (6, 4), (5, 5), (7, 5))

如何有效地完成这项工作？问候.

Answer 1

因为它们看起来像你可以使用的正确的python元组literal_eval.它安全快捷:

安全地评估表达式节点或包含Python表达式的字符串.提供的字符串或节点可能只包含以下Python文字结构:字符串,数字,元组,列表,dicts,布尔值和None.

import ast
s = '''(0, 0), (0, 2), ...'''
result = ast.literal_eval('({0})'.format(s))

Answer 2

假设有file.txt以下内容:

(0, 0), (0, 2), (0, 4), (-1, -1), (0, -2), (1, -1), (-1, -3)
(-1, 1), (-1, 3), (1, 1), (1, 3), (1, 5), (2, 0), (2, 2), (3, 3),
(2, 4), (3, 5), (4, 4), (5, 3), (6, 4), (5, 5), (7, 5)

您可以literal_eval()在循环中的每一行上使用并扩展结果列表:

from ast import literal_eval

result = []
with open('file.txt', 'r') as f:
    for line in f:
        result.extend(literal_eval(line.strip()))

print result

打印:

[(0, 0), (0, 2), (0, 4), (-1, -1), (0, -2), (1, -1), (-1, -3), (-1, 1), (-1, 3), (1, 1), (1, 3), (1, 5), (2, 0), (2, 2), (3, 3), (2, 4), (3, 5), (4, 4), (5, 3), (6, 4), (5, 5), (7, 5)]

仅供参考,literal_eval()是安全的:

安全地评估表达式节点或包含Python表达式的字符串.提供的字符串或节点可能只包含以下Python文字结构:字符串,数字,元组,列表,dicts,布尔值和None.

希望有所帮助.