【发布时间】：2021-04-22 03:50:10
【问题描述】：
我有一个庞大的数据集，包含大约 4 亿条记录，这些记录将记录从行转置到列。
输入数据集：
+------+------------------------------------------------------------------+----------------------------------+--+
| HHID | VAL_CD64 | VAL_CD32 | |
+------+------------------------------------------------------------------+----------------------------------+--+
| 203 | 8c5bfd9b6755ffcdb85dc52a701120e0876640b69b2df0a314dc9e7c2f8f58a5 | 373aeda34c0b4ab91a02ecf55af58e15 | |
| 203 | 0511dc19cb09f8f4ba3d140754dafb1471dacdbb6747cdb5a2bc38e278d229c8 | 6f3606577eadacef1b956307558a1efd | |
| 203 | a18adc1bcae1b570a610b13565b82e5647f05fef8a4680bd6ccdd717cdd34af7 | 332321ab150879e930869c15b1d10c83 | |
| 720 | f6c581becbac4ec1291dc4b9ce566334b1cb2c85e234e489e7fd5e1393bd8751 | 2c4f97a04f02db5a36a85f48dab39b5b | |
| 720 | abad845107a699f5f99575f8ed43e0440d87a8fc7229c1a1db67793561f0f1c3 | 2111293e946703652070968b224875c9 | |
| 348 | 25c7cf022e6651394fa5876814a05b8e593d8c7f29846117b8718c3dd951e496 | 5c80a555fcda02d028fc60afa29c4a40 | |
| 348 | 67d9c0a4bb98900809bcfab1f50bef72b30886a7b48ff0e9eccf951ef06542f9 | 6c10cd11b805fa57d2ca36df91654576 | |
| 348 | 05f1e412e7765c4b54a9acfd70741af545564f6fdfe48b073bfd3114640f5e37 | 6040b29107adf1a41c4f5964e0ff6dcb | |
| 403 | 3e8da3d63c51434bcd368d6829c7cee490170afc32b5137be8e93e7d02315636 | 71a91c4768bd314f3c9dc74e9c7937e8 | |
+------+------------------------------------------------------------------+----------------------------------+--+
输出数据集：
+------+------------------------------------------------------------------+------------------------------------------------------------------+------------------------------------------------------------------+----------------------------------+----------------------------------+----------------------------------+--+
| HHID | VAL1_CD64 | VAL2_CD64 | VAL3_CD64 | VAL1_CD32 | VAL2_CD32 | VAL3_CD32 | |
+------+------------------------------------------------------------------+------------------------------------------------------------------+------------------------------------------------------------------+----------------------------------+----------------------------------+----------------------------------+--+
| 203 | 8c5bfd9b6755ffcdb85dc52a701120e0876640b69b2df0a314dc9e7c2f8f58a5 | 0511dc19cb09f8f4ba3d140754dafb1471dacdbb6747cdb5a2bc38e278d229c8 | a18adc1bcae1b570a610b13565b82e5647f05fef8a4680bd6ccdd717cdd34af7 | 373aeda34c0b4ab91a02ecf55af58e15 | 6f3606577eadacef1b956307558a1efd | 332321ab150879e930869c15b1d10c83 | |
| 720 | f6c581becbac4ec1291dc4b9ce566334b1cb2c85e234e489e7fd5e1393bd8751 | abad845107a699f5f99575f8ed43e0440d87a8fc7229c1a1db67793561f0f1c3 | | 2c4f97a04f02db5a36a85f48dab39b5b | 2111293e946703652070968b224875c9 | | |
| 348 | 25c7cf022e6651394fa5876814a05b8e593d8c7f29846117b8718c3dd951e496 | 67d9c0a4bb98900809bcfab1f50bef72b30886a7b48ff0e9eccf951ef06542f9 | 05f1e412e7765c4b54a9acfd70741af545564f6fdfe48b073bfd3114640f5e37 | 5c80a555fcda02d028fc60afa29c4a40 | 6c10cd11b805fa57d2ca36df91654576 | 6040b29107adf1a41c4f5964e0ff6dcb | |
| 403 | 3e8da3d63c51434bcd368d6829c7cee490170afc32b5137be8e93e7d02315636 | | | 71a91c4768bd314f3c9dc74e9c7937e8 | | | |
+------+------------------------------------------------------------------+------------------------------------------------------------------+------------------------------------------------------------------+----------------------------------+----------------------------------+----------------------------------+--+
我目前的 Python 代码是：
import pandas as pd
import os
import shutil
import glob
import time
start=time.time()
print('\nFile Processing Started\n')
path=r'Sample Data'
input_file=r'test'
output_file=r'test_MOD'
chunk=pd.read_csv(input_file+'.psv',sep='|',chunksize=400000,dtype={"HHID":"string","VAL_CD64":"string","VAL_CD32":"string"})
chunk_list=[]
for c_no in chunk:
chunk_list.append(c_no)
file_no=1
rec_cnt=0
for i in chunk_list:
start2=time.time()
rec_cnt=rec_cnt+len(i)
rec_cnt2=0
rec_cnt2=len(i)
df=pd.DataFrame(i)
df_ = df.groupby('HHID').agg({'VAL_CD64': list, 'VAL_CD32': list})
data = []
for col in df_.columns:
d = pd.DataFrame(df_[col].values.tolist(), index=df_.index)
d.columns = [f'{col}_{i}' for i in map(str, range(1, len(d.columns)+1))]
data.append(d)
res = pd.concat(data, axis=1)
res.to_csv(output_file+str(file_no)+'.psv',index=True,sep='|')
with open(output_file+str(file_no)+'.psv','r') as istr:
with open(input_file+str(file_no)+'.psv','w') as ostr:
for line in istr:
line=line.strip('\n')+'|'
print(line,file=ostr)
os.remove(output_file+str(file_no)+'.psv')
file_no+=1
end2=time.time()
duration2=end2-start2
print("\nProcessed "+ str(rec_cnt2)+ " records in "+ str(round((duration2),2))+ " seconds. \nTotal Processed Records: "+str(rec_cnt))
os.remove(input_file+'.psv')
allFiles = glob.glob(path + "/*.psv")
allFiles.sort() # glob lacks reliable ordering, so impose your own if output order matters
with open(os.path.join(path,'someoutputfile.csv'), 'wb') as outfile:
for i, fname in enumerate(allFiles):
with open(fname, 'rb') as infile:
if i != 0:
infile.readline() # Throw away header on all but first file
# Block copy rest of file from input to output without parsing
shutil.copyfileobj(infile, outfile)
test=os.listdir(path)
for item in test:
if item.endswith(".psv"):
os.remove(os.path.join(path,item))
final_file_name=input_file+'.psv'
os.rename(os.path.join(path,'someoutputfile.csv'),final_file_name)
end=time.time()
duration=end-start
print("\n"+ str(rec_cnt)+ " records added in "+ str(round((duration),2))+ " seconds. \n")
但是，此脚本需要大量时间来处理记录。处理一个 4 亿条记录文件需要 16 个小时。
有什么办法可以减少执行时间，加快整个流程？
【问题讨论】：
标签： python python-3.x pandas