Python 逐行读取文件并转换为字典

Question

I have below data in file.sec:

goog,100
goog,101
goog,103
micro,200
micro,201
face,99

I want to convert this data into a dictionary: {'goog': [100,101,103], 'micro': [200, 201], 'face': [99]}

I tried below code, but it wipes out the list whenever value changes from goog to micro and result I get is: {'goog': [99], 'micro': [99], 'face':[99]}

allD = {}
allN = []
f = open('file.sec' , 'r')
for data in f:
   com = data.split(',')[0]
   
   if com not in allD.keys():
      del allN[:]

   allN.append( data.split(',')[1] )

   allD[ com ] = allN  
    
 print allD        

Answer 1

You could use defaultdict

from collections import defaultdict

result = defaultdict(list)

f = open('file.sec' , 'r')
for data in f:
    com = data.split(',')[0]
    result[com].append(data.split(',')[1]

Answer 2

You could use a defaultdict to solve this:

from collections import defaultdict

data_dict = defaultdict(list)

f = open('file.sec' , 'r')
for data in f:
    key, value = data.split(',')
    data_dict[key].append(value)

Note that i've written this in python 3 syntax, so you may need to do it slightly differently for python 2.

Answer 3

You are not far, but there is a misunderstanding on what a Python assignment is. When you write allD[ com ] = allN , allD[com] is not a copy of allN but is just another reference to the very same object. So when you later clean allN with del allN[:] you actually clean the last allD[com] . You should instead use a new object:

allD = {}
allN = []
f = open('file.sec' , 'r')
for data in f:
   com = data.split(',')[0]
   
   if com not in allD.keys():
      allN = []
      allD[ com ] = allN  

   allN.append( data.split(',')[1] )

    
 print allD

Answer 4

An example without defaultdict:

allD = {}
allN = []
f = open('data.csv', 'r')
for data in f:
    com = data.split(',')[0]

    if com not in allD.keys():
        allD[com] = []

    allD[com].append(data.split(',')[1].strip())

print(allD)