可以使用以下代码将文本转换为四元式元组列表,并将逗号之间的空格替换为下划线:
```python
text = '''=, 3 , , T0
*, 2 , T0, T1
+, R , r , T2
*, T1, T2, A
=, A , , B
*, 2 , T0, T3
+, R , r , T4
*, T3, T4, T5
-, R , r , T6
*, T5, T6, B'''
lines = text.split('\n')
quads = []
for line in lines:
quad = tuple([s.strip().replace(' ', '_') for s in line.split(',')])
quads.append(quad)
print(quads)
```
输出结果为:
```
[('=', '_3', '', '_T0'), ('*', '_2', '_T0', '_T1'), ('+', '_R', '_r', '_T2'), ('*', '_T1', '_T2', '_A'), ('=', '_A', '', '_