read_table pandas python数字错误

Question

I am doing a basic pd.read_table of a .txt file. The first column is a list of cusips. The cusip "65248E10" is being read as a number 65248E10 = 652480000000000 (E10 as scientific notation).

I have been going through the pandas but I can't figure out how to require it to stay as a character. http://pandas.pydata.org/pandas-docs/dev/generated/pandas.io.parsers.read_table.html#pandas.io.parsers.read_table

Also, even if I put header = 0, it seems to be putting the first row as the headers and then row 0 is the second row and so on. If my text file has no column names, how can I get that to default to NULL (or 1, 2, 3, etc.)

Thanks for the help. I am new to pandas/python

Answer 1

If we have a data file which looks like

65248E10 11
55555E55 22

then we can read it in with something like

>>> pd.read_table("cusip.txt", header=None, delimiter=" ", converters={0: str})
          0   1
0  65248E10  11
1  55555E55  22

where we use header=None to tell it that there aren't any headers, we use delimiter=" " to tell it there's a space delimiter (adjust to match your data format), and converters={0: str} to tell it that after reading the first column in as a string, we want to turn it into a string (ie in this case do nothing to it) rather than process it further. Instead of converters={0: str} , dtype=(str, int) would have worked too, but this way we can still let pandas figure out what the other columns are.

The problem with using header=0 is that 0 here doesn't mean "no header", it means use row number #0 (the first row) as the headers.

Answer 2

To stop your column from being read as a number, use the converters parameter and specify str as the converter for the column containing your "cusips".

For the header, as documented on the page you linked to, header is the number of the row which is to be considered the header; it is not a boolean saying "do I have a header or not. Setting it to zero means to use row zero (ie, the first row) as the header. The documentation explicitly says:

Specify None if there is no header row.