python将OpenDap加载到NetcdfFile [英] python load OpenDap to NetcdfFile

问题描述

我正在使用URL从opendap服务器打开netcdf数据(数据的子集).当我打开它时(据我所知)，直到请求该变量之前，才实际加载数据.我想将数据保存到磁盘上的文件中，该怎么办?

I am opening netcdf data from an opendap server (a subset of the data) using an URL. When I open it the data is (as far as I can see) not actually loaded until the variable is requested. I would like to save the data to a file on disk, how would I do this?

我目前有:

import numpy as np
import netCDF4 as NC

url = u'http://etc/etc/hourly?varname[0:1:10][0:1:30]'
set = NC.Dataset(url) # I think data is not yet loaded here, only the "layout"
varData = set.variables['varname'][:,:] # I think data is loaded here

# now i want to save this data to a file (for example test.nc), set.close() obviously wont work

希望有人可以提供帮助，谢谢！

Hope someone can help, thanks!

推荐答案

这很简单；创建一个新的NetCDF文件，然后复制所需的任何内容:)幸运的是，在从输入文件复制正确的尺寸，NetCDF属性，...方面，这可以在很大程度上实现自动化.我快速编写了这个示例，输入文件也是本地文件，但是如果使用OPenDAP进行读取已经可以了，那么它应该以类似的方式工作.

It's quite simple; create a new NetCDF file, and copy whatever you want :) Luckily this can be automated for a large part, in copying the correct dimensions, NetCDF attributes, ... from the input file. I quickly coded this example, the input file is also a local file, but if the reading with OPenDAP already works, it should work in a similar way.

import netCDF4 as nc4

# Open input file in read (r), and output file in write (w) mode:
nc_in = nc4.Dataset('drycblles.default.0000000.nc', 'r')
nc_out = nc4.Dataset('local_copy.nc', 'w')

# For simplicity; copy all dimensions (with correct size) to output file
for dim in nc_in.dimensions:
    nc_out.createDimension(dim, nc_in.dimensions[dim].size)

# List of variables to copy (they have to be in nc_in...):
# If you want all vaiables, this could be replaced with nc_in.variables
vars_out = ['z', 'zh', 't', 'th', 'thgrad']

for var in vars_out:
    # Create variable in new file:
    var_in  = nc_in.variables[var]
    var_out = nc_out.createVariable(var, datatype=var_in.dtype, dimensions=var_in.dimensions)

    # Copy NetCDF attributes:
    for attr in var_in.ncattrs():
        var_out.setncattr(attr, var_in.getncattr(attr))

    # Copy data:
    var_out[:] = var_in[:]

nc_out.close()

希望，如果没有让我知道的话，它会有所帮助.

Hope it helps, if not let me know.

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