读取制表符分隔的文件，并将每一列分配给一个独立的变量

Question

The following python code reads a tab separated file which contains multiple columns. I have store each column in a separate variable then tried to store the column into a dictionary and print out the the values of the dictionary.

import csv
dic1={}
dic2={}
with open("Table.tsv") as samplefile:
    reader = csv.reader(samplefile, delimiter="\t")
    columns = zip(*reader)
    for column in columns:
        A, B, C, D = columns #store the columns into separate variables

dic1[A] = samplefile # storing a specific variable (column) into a dictionary 
print (dic1[A]) 

Problem: I am not able to print out the dictionary which contains the data of "A" column! Not sure how to solve this problem.

Error message: <closed file 'Table.tsv', mode 'r' at 0x7fef50ba0030>

Your help is appreciated,

Answer 1

In the following line

dic1[A] = samplefile 

you are assigning the file object named samplefile to the dictionary and are using the content of variable 'A' as key value. And you error message is not an error message, its python's string representation of the file object. The file object is closed, since you left the with context.

You have to actually assign the variables to the dictionary like so.

dic1['a'] = A

Maybe you want to reread some information about how dictionaries work. Have a look here: http://learnpythonthehardway.org/book/ex39.html

Answer 2

Others have explained the problem that you are seeing, but a better way of writing your code is to use csv.DictReader .

import csv

with open("Table.tsv") as samplefile:
    reader = csv.DictReader(samplefile, delimiter="\t")
    for row in reader:
        print row['A']

The above assumes that the first line of your csv file contains the column names. If not, pass a list of the column names to DictReader :

reader = csv.DictReader(samplefile, ['A', 'B', 'C', 'D'], delimiter="\t")

Answer 3

Python cares about indentation (understatement of the year!). You need to indent your "for in" code block once more to make it part of the "within" block.

Answer 4

You aren't getting an error message.

with open("Table.tsv") as samplefile:
..
dic1[A] = samplefile # storing a specific variable (column) into a dictionary 
print (dic1[A])

You open a file, put the file handle in a dictionary, then take it out and print it. Python prints it and you see the text representation of a closed file handle .