generating a different DictReader object from an existing Dictreader object [duplicate]

Question

I could really use some help here:

I import a csv file to python using the csv.DictReader() method and the data structure looks like this: {'first_name': 'John', 'last_name': 'Doe', 'email': '[email protected]'} {'first_name': 'Mary', 'last_name': 'Jane', 'email': '[email protected]'} {'first_name': 'John', 'last_name': 'Smith', 'email': '[email protected]'} {'first_name': 'Vera', 'last_name': 'Wang', 'email': '[email protected]'}

The result I want to have is to return another DictReader object in the shape of: {'first_name': 'John', 'last_name': 'Doe'}` {'first_name': 'Mary', 'last_name': 'Jane'} {'first_name': 'John', 'last_name': 'Smith'} {'first_name': 'Vera', 'last_name': 'Wang'} i.e., dropping the last key of 'email';

While I do know using the del DictReader_Object['email'] can do the job, but is there a way to select multiple keys/columns?

e.g., I have 10s of columns in the dataset but I only need two of the columns; if using del function I will have to write the other 8 columns; so I just want a way to select two cols directly.

Thanks for the help!

Answer 1

Edit: found a dupe afterwards, leaving answer as community edit in non the less.

---

You can create smaller dicts while reading from your DictReader, put them inside a list and use that in a similar fashion:

from csv import DictReader, DictWriter

# create data
data = []
fn = list("abcdef")
for k in fn:
    data.append([])
    for v in range(4):
        data[-1].append( (k,v))
# print(data, "\n")

# transpose
data = zip(*data)
dd = [dict(w) for w in data]
print(dd , "\n")

# write big dict file
with open("k.dict","w", newline="") as f:
    w = DictWriter(f, fieldnames=fn)
    w.writeheader()
    w.writerows(dd)
print(open("k.dict").read(), "\n")

# get small dicts from file
whatIwant = ("c","d")
result = []
with open("k.dict") as f:
    w = DictReader(f)
    for l in w:
        result.append( dict( (k,v) for k,v in l.items() if k in whatIwant))

print(result)

Output:

# data transposed as dict's 
[{'a': 0, 'b': 0, 'c': 0, 'd': 0, 'e': 0, 'f': 0}, 
 {'a': 1, 'b': 1, 'c': 1, 'd': 1, 'e': 1, 'f': 1}, 
 {'a': 2, 'b': 2, 'c': 2, 'd': 2, 'e': 2, 'f': 2}, 
 {'a': 3, 'b': 3, 'c': 3, 'd': 3, 'e': 3, 'f': 3}]

# file content
a,b,c,d,e,f
0,0,0,0,0,0
1,1,1,1,1,1
2,2,2,2,2,2
3,3,3,3,3,3
4,4,4,4,4,4 

# list of minified dicts after reading
[{'c': '0', 'd': '0'}, {'c': '1', 'd': '1'}, 
 {'c': '2', 'd': '2'}, {'c': '3', 'd': '3'}]

Edit: You can find more ways to do similar things in Python CSV DictReader ignore columns?