Summarize the points that you should be careful about when using it for yourself. Will be added sequentially.
When index_col is used when reading CSV, the index type is different from the dtype specification. It seems that it will be decided automatically.
import pandas as pd
#Example) input.csv
#ID,param1,param2
#0001,01,AAA
#0002,02,BBB
#0003,10,CCC
df = pd.read_csv("input.csv", dtype=object, index_col="ID")
#The type is specified as object, but only index becomes int type
#The leading 0 is missing
It seems that it is necessary to specify the index later in order to retain the type.
df = pd.read_csv("input.csv", dtype=object)
df.set_index("ID", inplace=True)
#Now you can keep the original data
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