大熊猫。 pd.read_csv KeyError：索引错误

Question

I'm working with CSV file with over million entries. I'm trying to read data for each candidate as a separate column. I was able to parse data for the first candidate but when I get to next candidate I'm getting error ['cand_nm'] not in index.

Here is the link to file: Link to data file

%matplotlib
import matplotlib.pyplot as plt
import pandas as pd
import numpy as np

First candidate

reader_bachmann = pd.read_csv('P00000001-ALL.csv', squeeze=True, low_memory=False, nrows=411 )
print(reader_bachmann)
cand_bachmann = reader_bachmann[["cand_nm"]] 
print(cand_bachmann)

Second candidate

reader_romney = pd.read_csv('P00000001-ALL.csv', skiprows=range(0,411) ,  na_filter =True, low_memory=False)
print(reader_romney)
cand_romney = reader_romney[["cand_nm"]] 
print(cand_romney)

Error message

KeyError: "['cand_nm'] not in index"

Answer 1

When you use skip_rows like that you lose the header. So you header for reader_romney is now row number 412. If this is the way you want to read the file you will need to store the header line to a list of strings and then pass that list as the names= kwarg. For example

r_bachman = pd.read_csv('P00000001-ALL.csv', squeeze=True, low_memory=False,
                        nrows=411 )
cols = r_bachman.columns
r_romney = pd.read_csv('P00000001-ALL.csv', skiprows=range(0,411),
                       na_filter =True, low_memory=False, names=cols)