python 替代扫描 ('file' , what=list(...)) 在 R

Question

我有以下格式的文件:

10000 
2
2
2
2
0.00
0.00
0 1

0.00
0.01
0 1
...

我想从这个文件创建一个数据框(跳过前 5 行)，如下所示:

x1   x2    y1  y2
0.00 0.00  0   1
0.00 0.01  0   1

所以行被转换为列(其中每三行也被分成两列，y1 和 y2)。

在 R 中，我按如下方式执行此操作:

df = as.data.frame(scan(".../test.txt", what=list(x1=0, x2=0, y1=0, y2=0), skip=5))

我正在寻找此 scan(file, what=list(...)) 函数的 python 替代品(pandas？)。它是否存在，或者我是否必须编写更扩展的脚本？

Answer 1

您可以跳过前 5 个，然后以 4 个为一组构建一个 Python 列表，然后将其放入 pandas 作为开始......如果 pandas 提供更好的东西，我不会感到惊讶:

from itertools import islice, izip_longest

with open('input') as fin:
    # Skip header(s) at start
    after5 = islice(fin, 5, None)
    # Take remaining data and group it into groups of 4 lines each... The
    # first 2 are float data, the 3rd is two integers together, and the 4th
    # is the blank line between groups... We use izip_longest to ensure we
    # always have 4 items (padded with None if needs be)...
    for lines in izip_longest(*[iter(after5)] * 4):
            # Convert first two lines to float, and take 3rd line, split it and
            # convert to integers
        print map(float, lines[:2]) + map(int, lines[2].split())

#[0.0, 0.0, 0, 1]
#[0.0, 0.01, 0, 1]