6.1 使用csv模塊來讀寫csv數(shù)據(jù)
- 我們有如下csv文件
~/ning-dashboard/tmp > cat test.csv 2m 56s
symbol,price,date
"A",30.3,"6/11/2022"
"B",30.1,"5/11/2022"
一、讀取CSV文件
- 可以使用csv模塊來解析csv文件
>>> import csv
>>> with open("test.csv") as f:
... f_csv = csv.reader(f)
... headers = next(f_csv)
... print(headers)
... for r in f_csv:
... print(r)
...
['symbol', 'price', 'date']
['A', '30.3', '6/11/2022']
['B', '30.1', '5/11/2022']
>>>
上面的row我們獲取的是一個數(shù)組，這樣想要拿到指定列的值，我們需要使用row[0],row[1]這樣，容易造成混淆
我們可以考慮使用命名元組
>>> import csv
>>> from collections import namedtuple
>>> with open("test.csv") as f:
... f_csv = csv.reader(f)
... headers = next(f_csv)
... row = namedtuple('row',headers)
... for r in f_csv:
... rl = row(*r)
... print(rl)
...
row(symbol='A', price='30.3', date='6/11/2022')
row(symbol='B', price='30.1', date='5/11/2022')
>>>
- 而且這樣我們就可以使用row.symbol等方式調(diào)用值，不會造成混淆
- namedtuple第一個參數(shù)row相當(dāng)于對象名，第二個參數(shù)，相當(dāng)于屬性列表，需要輸入一個元組
- 可使用如下方式進(jìn)行取值
>>> rl.symbol
'B'
>>> rl.price
'30.1'
>>> rl.date
'5/11/2022'
>>>
但是上述方法只適用于headers的值都是合法標(biāo)識符，如果不是，需要使用下劃線或者其它占位符代替
也可以使用如下方式將csv數(shù)據(jù)讀取為OrderedDict
>>> with open("test.csv") as f:
... f_csv = csv.DictReader(f)
... for row in f_csv:
... print(row)
...
OrderedDict([('symbol', 'A'), ('price', '30.3'), ('date', '6/11/2022')])
OrderedDict([('symbol', 'B'), ('price', '30.1'), ('date', '5/11/2022')])
>>> row['symbol']
'B'
>>> row['price']
'30.1'
>>>
二、寫入csv文件
>>> h = ["test","test2","test3"]
>>> d = [("1",2,3),("2",30,20)]
>>> with open("test1.csv",'w') as f:
... f_csv = csv.writer(f)
... f_csv.writerow(h)
... f_csv.writerows(d)
~/ning-dashboard/tmp > cat test1.csv
test,test2,test3
1,2,3
2,30,20
- 如果數(shù)據(jù)是數(shù)據(jù)字典結(jié)構(gòu)，也可以這樣處理
>>> import csv
>>> d = [("1",2,3),("2",30,20)]
>>> h = ["test","test2","test3"]
>>> with open("test2.csv",'w') as f:
... f_csv = csv.DictWriter(f,h)
... f_csv.writeheader()
... f_csv.writerows(d)
...
