python csv与字典操作

# encoding: utf-8
import csv

d1 = {'banana':3,'apple':4,'pear':1,'orange':2}
d2 = {'banana':3,'orange':2}
d3 = {}
d4 = {'apple':4,'banana':3,'pear':1,'orange':2}
headers = ['banana', 'apple','pear','orange']
datas = [d1,d2,d3,d4]
#newline=''避免出现空行
with open('result.csv', 'w', newline='') as f:
    # 标头在这里传入，作为第一行数据
    writer = csv.DictWriter(f, headers)
    writer.writeheader()
    for row in datas:
        writer.writerow(row)
    # 还可以写入多行
    #writer.writerows(datas)

with open('result.csv') as f:
    reader = csv.DictReader(f)
    print(type(reader))
    print(reader)
    for row in reader:
        print(row)
        print(row['banana'])

<class 'csv.DictReader'>
<csv.DictReader object at 0x00000000026009E8>
OrderedDict([('banana', '3'), ('apple', '4'), ('pear', '1'), ('orange', '2')])
3
OrderedDict([('banana', '3'), ('apple', ''), ('pear', ''), ('orange', '2')])
3
OrderedDict([('banana', ''), ('apple', ''), ('pear', ''), ('orange', '')])

OrderedDict([('banana', '3'), ('apple', '4'), ('pear', '1'), ('orange', '2')])
3

Process finished with exit code 0