如何在python中读取复杂数据？

Question

我试图读取结构不好的数据。看起来像这样

Generated by trjconv : P/L=1/400 t=   0.00000
11214
    1P1     aP1    1  80.48  35.36   4.25
    2P1     aP1    2  37.45   3.92   3.96
    3P2     aP2    3  18.53  -9.69   4.68
    4P2     aP2    4  55.39  74.34   4.60
    5P3     aP3    5  22.11  68.71   3.85
    6P3     aP3    6  -4.13  24.04   3.73
    7P4     aP4    7  40.16   6.39   4.73
    8P4     aP4    8  -5.40  35.73   4.85
    9P5     aP5    9  36.67  22.45   4.08
   10P5     aP5   10  -3.68 -10.66   4.18
Generated by trjconv : P/L=1/400 t=   1000.000
11214
    1P1     aP1    1  80.48  35.36   4.25
    2P1     aP1    2  37.45   3.92   3.96
    3P2     aP2    3  18.53  -9.69   4.68
    4P2     aP2    4  55.39  74.34   4.60
    5P3     aP3    5  22.11  68.71   3.85
    6P3     aP3    6  -4.13  24.04   3.73
    7P4     aP4    7  40.16   6.39   4.73
    8P4     aP4    8  -5.40  35.73   4.85
    9P5     aP5    9  36.67  22.45   4.08
   10P5     aP5   10  -3.68 -10.66   4.18
Generated by trjconv : P/L=1/400 t=   2000.000
11214
    1P1     aP1    1  80.48  35.36   4.25
    2P1     aP1    2  37.45   3.92   3.96
    3P2     aP2    3  18.53  -9.69   4.68
    4P2     aP2    4  55.39  74.34   4.60
    5P3     aP3    5  22.11  68.71   3.85
    6P3     aP3    6  -4.13  24.04   3.73
    7P4     aP4    7  40.16   6.39   4.73
    8P4     aP4    8  -5.40  35.73   4.85
    9P5     aP5    9  36.67  22.45   4.08
   10P5     aP5   10  -3.68 -10.66   4.18
Generated by trjconv : P/L=1/400 t=   3000.000
11214
    1P1     aP1    1  80.48  35.36   4.25
    2P1     aP1    2  37.45   3.92   3.96
    3P2     aP2    3  18.53  -9.69   4.68
    4P2     aP2    4  55.39  74.34   4.60
    5P3     aP3    5  22.11  68.71   3.85
    6P3     aP3    6  -4.13  24.04   3.73
    7P4     aP4    7  40.16   6.39   4.73
    8P4     aP4    8  -5.40  35.73   4.85
    9P5     aP5    9  36.67  22.45   4.08
   10P5     aP5   10  -3.68 -10.66   4.18

它由具有更新时间的不同帧组成。我在这里展示的只是一个样本。整个文件大约为50GB。因此，最好逐行或分块阅读。但我不知道如何处理每个帧的标题。有没有办法去掉这些标题？目前，我使用了以下方法：

import numpy as np

#define a np.dtype for gro array/dataset (hard-coded for now)
gro_dt = np.dtype([('col1', 'S4'), ('col2', 'S4'), ('col3', int), 
                   ('col4', float), ('col5', float), ('col6', float)])

file = np.genfromtxt('sample.gro', skip_header = 2, dtype=gro_dt)

但是当它进入下一个标题时，会抛出以下错误

ValueError: Some errors were detected !
    Line #13 (got 7 columns instead of 6)
    Line #14 (got 1 columns instead of 6)
    Line #25 (got 7 columns instead of 6)
    Line #26 (got 1 columns instead of 6)
    Line #37 (got 7 columns instead of 6)
    Line #38 (got 1 columns instead of 6)

Answer 1

既然genfromtxt接受一个生成器函数，那么像这样的转换器函数也可以吗？（这将保持头中的t=值作为第一列保持不变。）

def converter(inf):
    current_t = None
    for line in inf:
        if "trjconv" in line:
            current_t = line.partition("t=")[-1].strip()
        elif line.startswith("  "):
            yield current_t + line


gro_dt = np.dtype(
    [
        ("t", "float"),
        ("col1", "S4"),
        ("col2", "S4"),
        ("col3", int),
        ("col4", float),
        ("col5", float),
        ("col6", float),
    ]
)


with open("sample.gro") as fp:
    file = np.genfromtxt(converter(fp), dtype=gro_dt)

print(file)

输出开始

[(   0., b'1P1', b'aP1',  1, 80.48,  35.36, 4.25)
 (   0., b'2P1', b'aP1',  2, 37.45,   3.92, 3.96)
 (   0., b'3P2', b'aP2',  3, 18.53,  -9.69, 4.68)
 (   0., b'4P2', b'aP2',  4, 55.39,  74.34, 4.6 )
 (   0., b'5P3', b'aP3',  5, 22.11,  68.71, 3.85)
 (   0., b'6P3', b'aP3',  6, -4.13,  24.04, 3.73)
 (   0., b'7P4', b'aP4',  7, 40.16,   6.39, 4.73)
 (   0., b'8P4', b'aP4',  8, -5.4 ,  35.73, 4.85)
 (   0., b'9P5', b'aP5',  9, 36.67,  22.45, 4.08)
 (   0., b'10P5', b'aP5', 10, -3.68, -10.66, 4.18)
 (1000., b'1P1', b'aP1',  1, 80.48,  35.36, 4.25)
 (1000., b'2P1', b'aP1',  2, 37.45,   3.92, 3.96)
 (1000., b'3P2', b'aP2',  3, 18.53,  -9.69, 4.68)
 (1000., b'4P2', b'aP2',  4, 55.39,  74.34, 4.6 )

Answer 2

编写一个适配器来剥离定期标题

def adapt(f):
    for line in f:
        if line.startswith("Generated"):
            print(line, end='')
            # Consume the following line as well.
            # If your data is well behaved, you can 
            # assume the following line exists and should be
            # skipped, instead of using the try statement.
            try:
                print(next(f), end='')
            except StopIteration:
                pass
            continue
        yield line

with open('sample.gro') as f:
    file = np.genfromtxt(adapt(f), dtype=gro_dt)

Answer 3

假设您想要收集帧数据（不确定您是否可以在50 GB的情况下收集）
下面的代码就是这样做的

def _is_interesting_line(line_str: str) -> bool:
    return line and line_str[0].isspace()


data = []
with open('data.txt') as f:
    while True:
        line = f.readline()
        if not line:
            break
        interesting = _is_interesting_line(line)
        if not interesting:
            print(line.strip())
        else:
            data.append(line.strip())
print('result:')
print(data)