我有一些性能和'丑陋的代码'的问题,也许你可以帮助一些。 我必须导出数据从netCDF文件到* .csv。为此,我编写了一些python代码。让我们拿一个3-dim netcdf文件:netCDF to * .csv without Loops(!)
def to3dim_csv():
var = ncf.variables['H2O'] #e.g. data for 'H2O' values
one,two,three = var.shape #variable dimension shape e.g. (551,42,94)
dim1,dim2,dim3 = var.dimensions #dimensions e.g. (time,lat,lon)
if crit is not None:
bool1 = foo(dim1,crit,ncf) #boolean table: ("value important?",TRUE,FALSE)
bool2 = foo(dim2,crit,ncf)
bool3 = foo(dim3,crit,ncf)
writer.writerow([dim1,dim2,dim3,varn])
for i in range(one):
for k in range(two):
for l in range(three):
if bool1[i] and bool2[k] and bool3[l]:
writer.writerow([
ncf.variables[dim1][i],
ncf.variables[dim2][k],
ncf.variables[dim3][l],
var[i,k,l],
])
ofile.close()
# Sample csv output is like:
# time,lat,lon,H2O
# 1,90,10,100
# 1,90,11,90
# 1,91,10,101
我想删除for val in range(d):
块。也许使用recursiv功能,如:
var = ncf.variables['H2O']
dims = [d for d in var.dimensions]
shapes = [var.variables[d].shape for d in dims]
bools = [bool_table(d,crit,ncf) for d in dims]
dims.append('H2O')
writer.writerow(dims)
magic_function(data)
def magic_function(data):
[enter code]
writer.writerow(data)
magic_function(left_data)
更新: 对于任何人谁是有兴趣的。此作品瞬间...
def data_to_table(dataset, var):
assert isinstance(dataset,xr.Dataset), 'Dataset must be xarray.Dataset'
obj = getattr(dataset, var)
table = np.zeros((obj.data.size, obj.data.ndim+1), dtype=np.object_)
table[:,0] = obj.data.flat
for i,d in enumerate(obj.dims):
repeat = np.prod(obj.data.shape[i+1:])
tile = np.prod(obj.data.shape[:i])
dim = getattr(dataset, d)
dimdata = dim.data
dimdata = np.repeat(dimdata, repeat)
dimdata = np.tile(dimdata, tile)
table[:,i+1] = dimdata.flat
return table
def export_to_csv(dataset, var, filename, size=None):
obj = getattr(dataset, var)
header = [var] + [x for x in obj.dims]
tabular = data_to_table(dataset, var)
size = slice(None,size,None) if size else slice(None,None,None)
with open(filename, 'w') as f:
writer = csv.writer(f,dialect=csv.excel)
writer.writerow(header)
writer.writerows(tabular[size])
1.如果我必须重复每个n-dim的代码,它看起来很丑。 2.需要花费大量的时间来浏览所有的数据。也许有人有一个使用'ncdump'或类似的功能来提高速度的想法 - [这个评论被删除我回答] – ucyo
使用递归函数在这里不会带来性能增益 – goncalopp
数组的numpy布尔索引应该加快速度? – M4rtini