Python numpy loadtxt 跳过第一行
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numpy loadtxt skip first row
提问by astromax
I have a small issue when I'm trying to import data from CSV files with numpy's loadtxt function. Here's a sample of the type of data files I have.
当我尝试使用 numpy 的 loadtxt 函数从 CSV 文件导入数据时遇到一个小问题。这是我拥有的数据文件类型的示例。
Call it 'datafile1.csv':
称之为“datafile1.csv”：
# Comment 1
# Comment 2
x,y,z
1,2,3
4,5,6
7,8,9
...
...
# End of File Comment
The script that I thought would work for this situation looks like:
我认为适用于这种情况的脚本如下所示：
import numpy as np
FH = np.loadtxt('datafile1.csv',comments='#',delimiter=',',skiprows=1)
But, I'm getting an error:
但是，我收到一个错误：
ValueError: could not convert string to float: x
This tells me that the kwarg 'skiprows' is not skipping the header, it's skipping the first row of comments. I could simply make sure that skiprows=3, but the complication is that I have a very large number of files, which don't all necessarily have the same number of commented lines at the top of the file. How can I make sure that when I use loadtxt I'm only getting the actual data in a situation like this?
这告诉我 kwarg 'skiprows' 没有跳过标题，而是跳过第一行评论。我可以简单地确保skiprows=3，但复杂的是我有大量的文件，这些文件的顶部不一定有相同数量的注释行。如何确保在使用 loadtxt 时仅在这种情况下获取实际数据？
P.S. - I'm open to bash solutions, too.
PS - 我也愿意接受 bash 解决方案。
采纳答案by falsetru
Skip comment line manually using generator expression:
使用生成器表达式手动跳过注释行：
import numpy as np
with open('datafile1.csv') as f:
lines = (line for line in f if not line.startswith('#'))
FH = np.loadtxt(lines, delimiter=',', skiprows=1)
回答by Jon Clements
Create your own custom filter function, such as:
创建您自己的自定义过滤器功能，例如：
def skipper(fname):
with open(fname) as fin:
no_comments = (line for line in fin if not line.lstrip().startswith('#'))
next(no_comments, None) # skip header
for row in no_comments:
yield row
a = np.loadtxt(skipper('your_file'), delimiter=',')
回答by JeffZheng
def skipper(fname, header=False):
with open(fname) as fin:
no_comments = (line for line in fin if not line.lstrip().startswith('#'))
if header:
next(no_comments, None) # skip header
for row in no_comments:
yield row
a = np.loadtxt(skipper('your_file'), delimiter=',')
This is just a little modification of @Jon Clements's answer by adding an optional parameter "header", given that in some cases, the csv file has comment lines (starts with #) but doesn't have the header row.
考虑到在某些情况下，csv 文件具有注释行（以 # 开头）但没有标题行，这只是对 @Jon Clements 的答案的一个小小的修改，添加了一个可选参数“header”。
