Python字典到CSV

Question

我编写了将CSV读入python字典的代码,工作正常.我正在尝试将字典恢复为CSV格式.我写了以下内容:

import csv

itemDict={}

listReader = csv.reader(open('/Users/broberts/Desktop/Sum_CSP1.csv','rU'), delimiter = ',', quotechar='|')

for row in listReader:
    fID = row[0]
    fClassRange = row[1]
    fArea = row[2]

    if itemDict.has_key(fID):
        itemDict[fID][fClassRange]=fArea
    else:
        itemDict[fID] = {'5.0 to 5.25':'','5.25 to 5.5':'','5.5 to 5.75':'','5.75 to 6.0':'','6.0 to 6.25':'','6.25 to 6.5':'','6.5 to 6.75':'','6.75 to 7.0':'','7.0 to 7.25':'','7.25 to 7.5':'','7.5 to 7.75':'','7.75 to 8.0':'','8.0 to 8.25':'',}
        itemDict[fID][fClassRange]=fArea

listWriter = csv.writer(open('/Users/broberts/Desktop/Sum_CSP1_output.csv', 'wb'), delimiter=',', quotechar='|', quoting=csv.QUOTE_MINIMAL)

for a in itemDict:
    print a
    listWriter.writerow(a)

在最后一个块中,listWriter不会向CSV写入任何内容,尽管它会打印出来.我相信这与字典无序有关.我真的需要写出fID和每个fID相关的每个键(fClassRange ex."5.0到5.25"),然后写出与每个fClassRange相关联的值fArea到CSV,但我还没有得到那么多我的代码,因为我无法弄清楚如何写出甚至fID.

我查看了使用DictWriter,但我无法弄清楚如何告诉它所需的字段名是什么.

Answer 1

默认编写者需要一个列表,这就是为什么它不适合你.要使用dictwriter,只需将您的listwriter =行更改为:

with open('/Users/broberts/Desktop/Sum_CSP1_output.csv', 'wb') as outfile:
    listWriter = csv.DictWriter(
       outfile,
       fieldnames=itemDict[itemDict.keys()[0]].keys(),
       delimiter=',',
       quotechar='|',
       quoting=csv.QUOTE_MINIMAL
    )

或者,如果您知道字段应该是什么,您可以设置fieldnames为fieldnames=['arbitrary','list','of','keys'].

Answer 2

样本数据:

mydict = [{"col1": 1000, "col2": 2000}, {"col1": 3000, "col2": 4000}]

使用pandas将单词列表转换为CSV的单行程序:

import pandas as pd

pd.DataFrame(mydict).to_csv('out.csv', index=False)

结果:

col1,col2
1000,2000
3000,4000

Answer 3

一个writerows的例子：

import csv

def main():

    results = [
            {'File': 'test.txt', 'Temperature': 32.33, 'Day': 'Monday'},
            {'File': 'test2.txt', 'Temperature': 44.33, 'Day': 'Tuesday'},
            {'File': 'test3.txt', 'Temperature': 44.23, 'Day': 'Sunday'}
        ]

    with open('results.csv', 'w') as f:  
        w = csv.DictWriter(f, results[0].keys())
        w.writeheader()        
        w.writerows(results)                    
        
if __name__ == "__main__":
    main()  

这将导致results.csv：

File,Temperature,Day
test.txt,32.33,Monday
test2.txt,44.33,Tuesday
test3.txt,44.23,Sunday