[英]How to iterate over each individual column values in multiple column dataframe?
I have multiple column data frame with columns ['Country', 'Energy Supply', 'Energy Supply per Capita', '% Renewable'] . 我有多个列数据框,其中列['国家','能源供应','人均能源供应','可再生%'] 。
In the energy supply column, I want to convert the unit of the column to Peta from Giga. 在能源供应栏中,我想将列的单位从千兆转换为Peta。 But in the process energy['Energy Supply']*= energy['Energy Supply']
, when the value is like "...." (missing value is denoted by this), is also getting multiplied or say duplicated. 但是在过程中energy['Energy Supply']*= energy['Energy Supply']
,当值类似于“......”(缺失值由此表示)时,也会增加或说重复。 Also, the string value in the column is also getting multiplied. 此外,列中的字符串值也会成倍增加。 (For eg original: Peta, after operation: PetaPetaPetaPeta...). (例如原版:Peta,术后:PetaPetaPetaPeta ......)。
To stop this from happening, I am running this: 为了阻止这种情况发生,我正在运行这个:
energy = pd.read_excel("Energy Indicators.xls",skiprows = 16, skip_footer = 38)
energy.drop(['Unnamed: 0','Unnamed: 1'],axis = 1, inplace = True)
energy.columns = ['Country', 'Energy Supply', 'Energy Supply per Capita', '% Renewable']
for i in energy['Energy Supply']:
if (isinstance(energy[i],int) == True):
energy['Energy Supply'][i]=energy['Energy Supply'][i]*1000000
return (energy)
But I am not getting the result ie to change the value of integer type variables only, and nothing is changing. 但我没有得到结果,即只改变整数类型变量的值,没有任何变化。
Where I think the problem lies in, the first two rows will give the false condition, as first rows are "String" and based on that, the program is not modifying the values, whereas I want to individually check if the value is of integer type and if it is, Multiplies the number by 1,000,000. 我认为问题在于,前两行将给出错误条件,因为第一行是“String”并且基于此,程序不修改值,而我想单独检查值是否为整数类型,如果是,则将数字乘以1,000,000。
Input: 输入:
Country Energy Supply Energy Supply per Capita % Renewable
0 NaN Petajoules Gigajoules %
1 Afghanistan 321 10 78.6693
2 Albania 102 35 100
3 Algeria 1959 51 0.55101
4 American Samoa ... ... 0.641026
Expected Output: 预期产出:
Country Energy Supply Energy Supply per Capita % Renewable
0 NaN Petajoules Gigajoules %
1 Afghanistan 3210000 10 78.6693
2 Albania 1020000 35 100
3 Algeria 19590000 51 0.55101
4 American Samoa ... ... 0.641026
Current Output: 电流输出:
Country Energy Supply Energy Supply per Capita % Renewable
0 NaN PetajoulesPeta. Gigajoules %
1 Afghanistan 3210000 10 78.6693
2 Albania 1020000 35 100
3 Algeria 19590000 51 0.55101
4 American Samoa ........ ... 0.641026
This worked for me with a million values: 这对我来说有一百万个值:
import pandas as pd
import numpy as np
data = {"Energy Supply":[1,30,"Petajoules",5,70]*2000000}
energy = pd.DataFrame(data)
input: 输入:
Energy Supply
0 1
1 30
2 Petajoules
3 5
4 70
5 1
6 30
7 Petajoules
8 5
9 70
10 1
11 30
12 Petajoules
13 5
14 70
15 1
16 30
17 Petajoules
18 5
19 70
20 1
21 30
22 Petajoules
23 5
24 70
25 1
26 30
27 Petajoules
28 5
29 70
...
[10000000 rows x 1 columns]
Then i transform the Series into an array and set the values: 然后我将Series转换为数组并设置值:
arr = energy["Energy Supply"].values
for i in range(len(arr)):
if isinstance(arr[i],int):
arr[i] = arr[i]*1000000
else:
pass
The output looks like this: 输出如下所示:
Energy Supply
0 1000000
1 30000000
2 Petajoules
3 5000000
4 70000000
5 1000000
6 30000000
7 Petajoules
8 5000000
9 70000000
10 1000000
11 30000000
12 Petajoules
13 5000000
14 70000000
15 1000000
16 30000000
17 Petajoules
18 5000000
19 70000000
20 1000000
21 30000000
22 Petajoules
23 5000000
24 70000000
25 1000000
26 30000000
27 Petajoules
28 5000000
29 70000000
...
[10000000 rows x 1 columns]
This solution is about twice as fast as an apply: 此解决方案的速度约为应用程序的两倍:
Looping through an array: 循环遍历数组:
loop: 100%|██████████| 10000000/10000000 [00:07<00:00, 1376439.75it/s]
Using Apply: 使用申请:
apply: 100%|██████████| 10000000/10000000 [00:14<00:00, 687420.00it/s]
If you convert the series to numeric then the string values become nan values. 如果将系列转换为数字,则字符串值将变为nan值。 Using np.where you need about 5 seconds for both converting the series to numeric and multiplying the values: 使用np.where,您需要大约5秒钟才能将系列转换为数字并乘以值:
import pandas as pd
import numpy as np
import time
data = {"Energy Supply":[1,30,"Petajoules",5,70]*2000000}
energy = pd.DataFrame(data)
t = time.time()
energy["Energy Supply"] = pd.to_numeric(energy["Energy Supply"],errors="coerce")
energy["Energy_Supply"] = np.where((energy["Energy Supply"]%1==0),energy["Energy Supply"]*100,energy["Energy Supply"])
t1 = time.time()
print(t1-t)
5.275099515914917
But you could also simply do this after using pd.to_numeric(): 但是您也可以在使用pd.to_numeric()后执行此操作:
energy["Energy Supply"] = energy["Energy Supply"]*1000000
You can use str.isnumeric
to check if a string is numeric and then multiply. 您可以使用str.isnumeric
检查字符串是否为数字,然后相乘。
energy['Energy Supply'] = energy['Energy Supply'].apply(lambda x: int(x) * 1000000 if str(x).isnumeric() else x)
print (energy)
Country Energy Supply Energy Supply per Capita % Renewable
0 NaN Petajoules Gigajoules %
1 Afghanistan 321000000 10 78.6693
2 Albania 102000000 35 100
3 Algeria 1959000000 51 0.55101
4 American Samoa ... .. 0.641026
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