pandas 熊猫将 dtype 对象转换为字符串
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Pandas converting dtype object to string
提问by nick appel
I have trouble converting the dtype of a column. I am loading a csv file from yahoo finance.
我在转换列的 dtype 时遇到问题。我正在从雅虎财经加载一个 csv 文件。
dt = pd.read_csv('data/Tesla.csv')
this gives me the following info:
这给了我以下信息：
<class 'pandas.core.frame.DataFrame'>
Int64Index: 923 entries, 0 to 922
Data columns (total 7 columns):
Date 923 non-null object
Open 923 non-null float64
High 923 non-null float64
Low 923 non-null float64
Close 923 non-null float64
Volume 923 non-null int64
Adj Close 923 non-null float64
dtypes: float64(5), int64(1), object(1)
i try to convert the Date into a string but whatever i try it doesn't working. I tried to loop over the row and convert it with str(). I have tried to change the dtype of the object with dt['Date'].apply(str)and I have tried a special dtype object and use that:
我尝试将日期转换为字符串，但无论我尝试什么都不起作用。我尝试遍历该行并使用 str() 对其进行转换。我试图改变对象的 dtypedt['Date'].apply(str)并且我尝试了一个特殊的 dtype 对象并使用它：
types={'Date':'str','Open':'float','High':'float','Low':'float','Close':'float','Volume':'int','Adj Close':'float'}
dt = pd.read_csv('data/Tesla.csv', dtype=types)
But nothing seems to be working.
但似乎没有任何效果。
I use pandas version 0.13.1
我使用Pandas版本 0.13.1
采纳答案by Wesley Bowman
Converting your dates into a DateTime will allow you to easily compare a user inputted date with the dates in your data.
将日期转换为 DateTime 将允许您轻松地将用户输入的日期与数据中的日期进行比较。
#Load in the data
dt = pd.read_csv('data/Tesla.csv')
#Change the 'Date' column into DateTime
dt['Date']=pd.to_datetime(dt['Date'])
#Find a Date using strings
np.where(dt['Date']=='2014-02-28')
#returns (array([0]),)
np.where(dt['Date']=='2014-02-21')
#returns (array([5]),)
#To get the entire row's information
index = np.where(dt['Date']=='2014-02-21')[0][0]
dt.iloc[index]
#returns:
Date 2014-02-21 00:00:00
Open 211.64
High 213.98
Low 209.19
Close 209.6
Volume 7818800
Adj Close 209.6
Name: 5, dtype: object
So if you wanted to do a for loop, you could create a list or numpy array of dates, then iterate through them, replacing the date in the index with your value:
因此，如果您想执行 for 循环，您可以创建一个日期列表或 numpy 数组，然后遍历它们，将索引中的日期替换为您的值：
input = np.array(['2014-02-21','2014-02-28'])
for i in input:
index = np.where(dt['Date']==i)[0][0]
dt.iloc[index]
