What is a very general way to read-in .csv in Pyth

问题:

I have a .csv file with rows with multiple columns lengths.

import pandas as pd
df = pd.read_csv(infile, header=None)

returns the

ParserError: Error tokenizing data. C error: Expected 6 fields in line 8, saw 8

error. I know I can use the

names=my_cols 

option in the read_csv call, but surely there has to be something more 'pythonic' than that?? Also, this is not a duplicate question, since

error_bad_lines=False 

causes lines to be skipped (which is not desired). The .csv looks like::

Anne,Beth,Caroline,Ernie,Frank,Hannah
Beth,Caroline,David,Ernie
Caroline,Hannah
David,,Anne,Beth,Caroline,Ernie
Ernie,Anne,Beth,Frank,George
Frank,Anne,Caroline,Hannah
George,
Hannah,Anne,Beth,Caroline,David,Ernie,Frank,George

回答1:

OK, somewhat inspired by this related question: Pandas variable numbers of columns to binary matrix

So read in the csv but override the separator to a tab so it doesn't try to split the names:

In[7]:
import pandas as pd
import io
t="""Anne,Beth,Caroline,Ernie,Frank,Hannah
Beth,Caroline,David,Ernie
Caroline,Hannah
David,,Anne,Beth,Caroline,Ernie
Ernie,Anne,Beth,Frank,George
Frank,Anne,Caroline,Hannah
George,
Hannah,Anne,Beth,Caroline,David,Ernie,Frank,George"""
df = pd.read_csv(io.StringIO(t), sep='\t', header=None)
df

Out[7]: 
                                                   0
0              Anne,Beth,Caroline,Ernie,Frank,Hannah
1                          Beth,Caroline,David,Ernie
2                                    Caroline,Hannah
3                    David,,Anne,Beth,Caroline,Ernie
4                       Ernie,Anne,Beth,Frank,George
5                         Frank,Anne,Caroline,Hannah
6                                            George,
7  Hannah,Anne,Beth,Caroline,David,Ernie,Frank,Ge...

We can now use str.split with expand=True to expand the names into their own columns:

In[8]:
df[0].str.split(',', expand=True)

Out[8]: 
          0         1         2         3         4       5      6       7
0      Anne      Beth  Caroline     Ernie     Frank  Hannah   None    None
1      Beth  Caroline     David     Ernie      None    None   None    None
2  Caroline    Hannah      None      None      None    None   None    None
3     David                Anne      Beth  Caroline   Ernie   None    None
4     Ernie      Anne      Beth     Frank    George    None   None    None
5     Frank      Anne  Caroline    Hannah      None    None   None    None
6    George                None      None      None    None   None    None
7    Hannah      Anne      Beth  Caroline     David   Ernie  Frank  George

So just to be clear modify your read_csv line to this:

df = pd.read_csv(infile, header=None, sep='\t')

and then do the str.split as above

回答2:

One can do some manipulation with the csv before using pandas.

# load data into list
with open('new_data.txt', 'r') as fil:
    data = fil.readlines()

# remove line breaks from string entries
data = [ x.replace('\r\n', '') for x in data]
data = [ x.replace('\n', '') for x in data]

# calculate the number of columns
total_cols = max([x.count(',') for x in data])

# add ',' to end of list depending on how many are needed
new_data = [x + ','*(total_cols-x.count(',')) for x in data]

# save data
with open('save_data.txt', 'w') as outp:
    outp.write('\n'.join(new_data))

# read it in as you did.
pd.read_csv('save_data.txt', header=None)

This is some rough python, but should work. I'll clean this up when I have time.

Or use the other answer, it's neat as it is.