PyGrADS示例

PyGrADS示例.

首先導入模塊:

from grads import *
from sys   import stdout

測試PyGrADS是否正確安裝:

try:
    ga = GrADS(Verb=1, Echo=False, Port=False, Window=False,Opts="-c 'q config'")
    print(">>> OK <<< start GrADS")
except:
    print(">>> NOT OK <<< cannot start GrADS")

嘗試打開一個控制文件,打印文件中的信息:

try:
    fh = ga.open("../data/model.ctl")
    print(fh.title)
    print('              File Id: ', fh.fid)
    print('         Dataset type: ', fh.type)
    print('    No. of Time steps: ', fh.nt)
    print('    No. of Longitudes: ', fh.nx)
    print('    No. of  Latitudes: ', fh.ny)
    print('    No. of     Levels: ', fh.nz)
    print('      Variable  names: ', fh.vars)
    print('      Variable levels: ', fh.var_levs)
    print('      Variable titles: ', fh.var_titles)
    print(">>> OK <<< open CTL file")
except:
    print(">>> NOT OK <<< cannot open CTL file")

讀取NetCDF文件時,會自動調用sdfopen:

try:
    fh = ga.open("../data/model.nc")
    print(fh.title)
    print ('              File Id: ', fh.fid)
    print ('         Dataset type: ', fh.type)
    print ('    No. of Time steps: ', fh.nt)
    print ('    No. of Longitudes: ', fh.nx)
    print ('    No. of  Latitudes: ', fh.ny)
    print ('    No. of     Levels: ', fh.nz)
    print ('      Variable  names: ', fh.vars)
    print ('      Variable levels: ', fh.var_levs)
    print ('      Variable titles: ', fh.var_titles)
    print (">>> OK <<< open NetCDF file")
except:
    print(">>> NOT OK <<< cannot open NetCDF file")

查詢維度信息(query dims):

try:
    qh = ga.query('dims')
    print('Current dimensional state: ')
    print ('   X is '+qh.x_state+'   Lon = ',qh.lon,'  X = ',qh.x)
    print('   Y is '+qh.y_state+'   Lat = ',qh.lat,'  Y = ',qh.y)
    print('   Z is '+qh.z_state+'   Lev = ',qh.lev,'  Z = ',qh.z)
    print('   T is '+qh.t_state+'  Time = ',qh.time,'  T = ',qh.t)
    print(">>> OK <<< query dimensions")
except:
    print(">>> NOT OK <<< cannot query dimensions")

查詢文件信息(query file):

try:
    qh = ga.query('file')
    print('Current file state: ')
    print('         Title: ', qh.title)
    print('       File Id: ', qh.fid)
    print('   Description: ', qh.desc)
    print('        Binary: ', qh.bin)
    print '   Variable  Num levels  Description')
    for (var, nlevels0,nlevels1, desc) in qh.var_info:
         print( '   '+var.rjust(8)+'  '+str(nlevels0).rjust(10)+str(nlevels1).rjust(10)+'  '+desc)
    print(">>> OK <<< query file")
except:
    print(">>> NOT OK <<< cannot query file")

測試捕獲grads輸出(Line和Word):

try:
    ga.cmd("q config")
    
    print("--------------------------------------------------------------")
    print "            Captured GrADS output: Line interface"
    print("--------------------------------------------------------------")
    for i in range(1,ga.nLines):
        print(ga.rline(i))

    print("--------------------------------------------------------------")
    print "            Captured GrADS output: Word interface"
    print("--------------------------------------------------------------")
    for i in range(1,ga.nLines):
        for j in range(1,20):     # 20 is an over estimate, but i is OK
            stdout.write(ga.rword(i,j)+' ')
        stdout.write('\n')

    print(">>> OK <<< rline()/rword() completes")
except:
    print(">>> NOT OK <<< rline()/rword() fails")

測試和Python交換變量,即可以將grads空間中的變量導入到python工作空間中,反之亦然:

try:
    ts = ga.exp('ts')
    print("Ts in Kelvins: ", ts.min(), ts.max())
    ts = ts - 273
    print("Ts in Celsius: ", ts.min(), ts.max())
    ga.imp('tc',ts)
    tc = ga.exp('tc')
    print("Tc in Celsius: ", tc.min(), tc.max())
    print(">>> OK <<< exp()/imp() completes")
except:
    print(">>> NOT OK <<< exp()/imp() fails")

執行批處理:

try:
    ga("""
           set lat 30 60
           set lon -80 -50
           set t 1 3
           query dims
       """)
    print(">>> OK <<< successfuly ran several commands at one")
except:
    print(">>> NOT OK <<< could not run several commands at once")