如何将此字典列表转换为csv文件?-Python 实用宝典

如何将此字典列表转换为csv文件?

我有一个字典列表,看起来像这样: toCSV = [{'name':'bob','age':25,'weight':200},{'name':'jim','age':31,'weight':180}] 我应该怎么做才能将其转换为如下所示的csv文件: name,age,weight bob,25,200 jim,31,180

问题:如何将此字典列表转换为csv文件?

我有一个字典列表,看起来像这样:

toCSV = [{'name':'bob','age':25,'weight':200},{'name':'jim','age':31,'weight':180}]

我应该怎么做才能将其转换为如下所示的csv文件:

name,age,weight
bob,25,200
jim,31,180

I have a list of dictionaries that looks something like this:

toCSV = [{'name':'bob','age':25,'weight':200},{'name':'jim','age':31,'weight':180}]

What should I do to convert this to a csv file that looks something like this:

name,age,weight
bob,25,200
jim,31,180

回答 0

import csv
toCSV = [{'name':'bob','age':25,'weight':200},
         {'name':'jim','age':31,'weight':180}]
keys = toCSV[0].keys()
with open('people.csv', 'wb') as output_file:
    dict_writer = csv.DictWriter(output_file, keys)
    dict_writer.writeheader()
    dict_writer.writerows(toCSV)

编辑:我以前的解决方案不处理订单。正如Wilduck所指出的,此处DictWriter更合适。

import csv
toCSV = [{'name':'bob','age':25,'weight':200},
         {'name':'jim','age':31,'weight':180}]
keys = toCSV[0].keys()
with open('people.csv', 'w', newline='')  as output_file:
    dict_writer = csv.DictWriter(output_file, keys)
    dict_writer.writeheader()
    dict_writer.writerows(toCSV)

EDIT: My prior solution doesn't handle the order. As noted by Wilduck, DictWriter is more appropriate here.


回答 1

这是当您有一个词典列表时:

import csv
with open('names.csv', 'w') as csvfile:
    fieldnames = ['first_name', 'last_name']
    writer = csv.DictWriter(csvfile, fieldnames=fieldnames)
    writer.writeheader()
    writer.writerow({'first_name': 'Baked', 'last_name': 'Beans'})

this is when you have one dictionary list:

import csv
with open('names.csv', 'w') as csvfile:
    fieldnames = ['first_name', 'last_name']
    writer = csv.DictWriter(csvfile, fieldnames=fieldnames)
    writer.writeheader()
    writer.writerow({'first_name': 'Baked', 'last_name': 'Beans'})

回答 2

在python 3中,情况有所不同,但是方式更简单,错误更少。最好告诉CSV文件应使用utf8编码打开,因为这会使数据更易于其他人使用(假设您未使用限制性更强的编码,例如latin1

import csv
toCSV = [{'name':'bob','age':25,'weight':200},
         {'name':'jim','age':31,'weight':180}]
with open('people.csv', 'w', encoding='utf8', newline='') as output_file:
    fc = csv.DictWriter(output_file, 
                        fieldnames=toCSV[0].keys(),

                       )
    fc.writeheader()
    fc.writerows(toCSV)
  • 请注意,csv在python 3中需要该newline=''参数,否则在excel / opencalc中打开时,CSV中会出现空白行。

或者:我更喜欢在pandas模块中使用csv处理程序。我发现它对编码问题的容忍度更高,并且熊猫在加载文件时会自动将CSV中的字符串数字转换为正确的类型(int,float等)。

import pandas
dataframe = pandas.read_csv(filepath)
list_of_dictionaries = dataframe.to_dict('records')
dataframe.to_csv(filepath)

注意:

  • 如果您提供路径,pandas将为您打开文件,并且默认为 utf8 python3中的名称,并且找出标头。
  • 数据框的结构与CSV所提供的结构不同,因此在加载时添加一行即可得到相同的结果: dataframe.to_dict('records')
  • 熊猫还使控制csv文件中列的顺序变得更加容易。默认情况下,它们是字母顺序的,但是您可以指定列顺序。使用香草csv模块,您需要将其喂入,OrderedDict否则它们将以随机顺序出现(如果在python <3.5中工作)。有关更多信息,请参见:在Python Pandas DataFrame中保留列顺序

In python 3 things are a little different, but way simpler and less error prone. It's a good idea to tell the CSV your file should be opened with utf8 encoding, as it makes that data more portable to others (assuming you aren't using a more restrictive encoding, like latin1)

import csv
toCSV = [{'name':'bob','age':25,'weight':200},
         {'name':'jim','age':31,'weight':180}]
with open('people.csv', 'w', encoding='utf8', newline='') as output_file:
    fc = csv.DictWriter(output_file, 
                        fieldnames=toCSV[0].keys(),

                       )
    fc.writeheader()
    fc.writerows(toCSV)
  • Note that csv in python 3 needs the newline='' parameter, otherwise you get blank lines in your CSV when opening in excel/opencalc.

Alternatively: I prefer use to the csv handler in the pandas module. I find it is more tolerant of encoding issues, and pandas will automatically convert string numbers in CSVs into the correct type (int,float,etc) when loading the file.

import pandas
dataframe = pandas.read_csv(filepath)
list_of_dictionaries = dataframe.to_dict('records')
dataframe.to_csv(filepath)

Note:

  • pandas will take care of opening the file for you if you give it a path, and will default to utf8 in python3, and figure out headers too.
  • a dataframe is not the same structure as what CSV gives you, so you add one line upon loading to get the same thing: dataframe.to_dict('records')
  • pandas also makes it much easier to control the order of columns in your csv file. By default, they're alphabetical, but you can specify the column order. With vanilla csv module, you need to feed it an OrderedDict or they'll appear in a random order (if working in python < 3.5). See: Preserving column order in Python Pandas DataFrame for more.

回答 3

因为@User和@BiXiC在这里寻求UTF-8的帮助,所以@Matthew提供了解决方案的变体。(不允许发表评论,所以我在回答。)

import unicodecsv as csv
toCSV = [{'name':'bob','age':25,'weight':200},
         {'name':'jim','age':31,'weight':180}]
keys = toCSV[0].keys()
with open('people.csv', 'wb') as output_file:
    dict_writer = csv.DictWriter(output_file, keys)
    dict_writer.writeheader()
    dict_writer.writerows(toCSV)

Because @User and @BiXiC asked for help with UTF-8 here a variation of the solution by @Matthew. (I'm not allowed to comment, so I'm answering.)

import unicodecsv as csv
toCSV = [{'name':'bob','age':25,'weight':200},
         {'name':'jim','age':31,'weight':180}]
keys = toCSV[0].keys()
with open('people.csv', 'wb') as output_file:
    dict_writer = csv.DictWriter(output_file, keys)
    dict_writer.writeheader()
    dict_writer.writerows(toCSV)

回答 4

import csv

with open('file_name.csv', 'w') as csv_file:
    writer = csv.writer(csv_file)
    writer.writerow(('colum1', 'colum2', 'colum3'))
    for key, value in dictionary.items():
        writer.writerow([key, value[0], value[1]])

这是将数据写入.csv文件的最简单方法

import csv

with open('file_name.csv', 'w') as csv_file:
    writer = csv.writer(csv_file)
    writer.writerow(('colum1', 'colum2', 'colum3'))
    for key, value in dictionary.items():
        writer.writerow([key, value[0], value[1]])

This would be the simplest way to write data to .csv file


回答 5

这是另一个更通用的解决方案,假设您没有行列表(也许它们不适合内存)或标题的副本(也许write_csv函数是通用的):

def gen_rows():
    yield OrderedDict(name='bob', age=25, weight=200)
    yield OrderedDict(name='jim', age=31, weight=180)

def write_csv():
    it = genrows()
    first_row = it.next()  # __next__ in py3
    with open("people.csv", "w") as outfile:
        wr = csv.DictWriter(outfile, fieldnames=list(first_row))
        wr.writeheader()
        wr.writerow(first_row)
        wr.writerows(it)

注意:这里使用的OrderedDict构造函数仅在python> 3.4中保留顺序。如果订单很重要,请使用OrderedDict([('name', 'bob'),('age',25)])表格。

Here is another, more general solution assuming you don't have a list of rows (maybe they don't fit in memory) or a copy of the headers (maybe the write_csv function is generic):

def gen_rows():
    yield OrderedDict(name='bob', age=25, weight=200)
    yield OrderedDict(name='jim', age=31, weight=180)

def write_csv():
    it = genrows()
    first_row = it.next()  # __next__ in py3
    with open("people.csv", "w") as outfile:
        wr = csv.DictWriter(outfile, fieldnames=list(first_row))
        wr.writeheader()
        wr.writerow(first_row)
        wr.writerows(it)

Note: the OrderedDict constructor used here only preserves order in python >3.4. If order is important, use the OrderedDict([('name', 'bob'),('age',25)]) form.


回答 6

import csv
toCSV = [{'name':'bob','age':25,'weight':200},
         {'name':'jim','age':31,'weight':180}]
header=['name','age','weight']     
try:
   with open('output'+str(date.today())+'.csv',mode='w',encoding='utf8',newline='') as output_to_csv:
       dict_csv_writer = csv.DictWriter(output_to_csv, fieldnames=header,dialect='excel')
       dict_csv_writer.writeheader()
       dict_csv_writer.writerows(toCSV)
   print('\nData exported to csv succesfully and sample data')
except IOError as io:
    print('\n',io)
import csv
toCSV = [{'name':'bob','age':25,'weight':200},
         {'name':'jim','age':31,'weight':180}]
header=['name','age','weight']     
try:
   with open('output'+str(date.today())+'.csv',mode='w',encoding='utf8',newline='') as output_to_csv:
       dict_csv_writer = csv.DictWriter(output_to_csv, fieldnames=header,dialect='excel')
       dict_csv_writer.writeheader()
       dict_csv_writer.writerows(toCSV)
   print('\nData exported to csv succesfully and sample data')
except IOError as io:
    print('\n',io)

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