Pandas to_sql() 插入索引
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Pandas to_sql() inserting index
提问by AlexanderMP
I am using Pandas 0.18.1, and while fiddling with this code,
我正在使用 Pandas 0.18.1，在摆弄这段代码的同时，
import pd
def getIndividualDf(item):
var1 = []
# ... populate this list of numbers
var2 = []
# ... populate this other list of numbers
newDf = pd.DataFrame({'var1': var1, 'var2': var2})
newDf['extra_column'] = someIntScalar
yield newDf
dfs = []
for item in someList:
dfs.append(getIndividualDf(item))
resultDf = pd.concat(dfs)
resultDf['segment'] = segmentId # this is an integer scalar
from sqlalchemy import create_engine
engine = create_engine('postgresql://'+user+':'+password+'@'+host+'/'+dbname)
resultDf.reset_index().to_sql('table_name', engine, schema="schema_name", if_exists="append", index=False)
I was getting this exception:
我收到此异常：
(psycopg2.ProgrammingError) column "index" of relation "table_name" does not exist
(psycopg2.ProgrammingError) 关系“table_name”的“index”列不存在
Indeed, there is no such column in the table, only because there is no such explicit column in the data frame. Which is why it's weird.
确实，表中没有这样的列，只是因为数据框中没有这样的显式列。这就是为什么它很奇怪。
Running
跑步
print(list(resultDf))
just before the to_sql()call, yields
就在to_sql()调用之前，产生
['var1', 'var2', 'extra_column', 'segment']
['var1', 'var2', 'extra_column', 'segment']
Removing index=Falsefrom the to_sql()call changes the error to this:
index=False从to_sql()调用中删除将错误更改为：
(psycopg2.ProgrammingError) column "level_0" of relation "table_name" does not exist
(psycopg2.ProgrammingError) 关系“table_name”的“level_0”列不存在
I am puzzled. How do I get rid of indexcolumn?
我很困惑。我如何摆脱index列？
Updateprint(resultDf.head())yielded this information:
更新print(resultDf.head())产生了以下信息：
var1 var2 extra_column segment
0 8 0.101653 2077869737 201606
1 9 0.303694 2077869737 201606
2 10 0.493210 2077869737 201606
3 11 0.661064 2077869737 201606
4 12 0.820924 2077869737 201606
回答by Steven G
You need not to reset the index before writing to sql such has:
您无需在写入 sql 之前重置索引，例如：
resultDf.to_sql('table_name', engine, schema="schema_name", if_exists="append", index=False)
