How to add dictionary items when I loop in python

Question

I am a beginner in python and I am trying to parse information from eml files in python. I set up my extract function to parse what I want to get. The problem is I have 10,000+ files and I don't know how to add every extracted information to one object.

When I run the extract function on one eml file, the output looks like

{'from': 'Joe', 'to': 'Robert', 'text': 'Hey Robert'}

The output is a dict object. Now I want to append my extracted ouput to my existing output ( name ) to collect every information from 10,000 files in name . How can I do this? I used following code, but the name object only has the information from last file in FList (which is a list of each 10,000+ files).

for i in range(len(FList)):
  f = open(FList[i])
  name=extract(f, f.name)
  f.close()

Answer 1

It looks like you want to map the filename to the dictionary with the data from the file. To do that, you'd do something like:

file_map = {}
for fname in FList:
    with open(fname) as f:
        file_map[fname] = extract(f, fname)

Answer 2

The name object is being overwritten in your loop. Since name is meant to be a dict, and dicts are passed by reference (google on pass by reference to get more info), you can do something like this:

names = dict()
for my_file in file_lst:
    with open(my_file) as f:
        extract(f,names)

def extract(f, names):
    #modify your names dict here such as:
    names["something new"] = "a new value"

After you are done with looping over file_lst you will have names populated with all the info from all files, as it will be retained across the loop...

Answer 3

It all depends on how you want to store your data. If you just want a list of entries, then you just need to append the extracted data to a list as follows:

name = []

for file_name in FList:
    with open(file_name) as f:
        name.append(extract(f, f.name))

In extract() , you could add another dictionary entry to hold the filename of the entry before returning it.