KeyError：1个python中的代码-无法找出问题

Question

This code used to work and no longer does. For the life of me can't figure out what is wrong. I am guessing it has to do with the for loop but that is about it.

import pandas as pd

LastFY = 2017
n = 15

DeclRate = 0.1
Res = 442.364
LFY_Vol = 27.8

Col_Names = ['Year', 'Reserves', 'Prod']
df = pd.DataFrame(columns=Col_Names)
df_add = pd.DataFrame(columns=Col_Names)

df['Year'] = [LastFY]
df['Prod'] = [LFY_Vol]
df['Reserves'] = [Res]

for i in range(1, n+1):

    FY = df['Year'][i-1] + 1
    if df['Prod'][i-1] * (1 - DeclRate) > df['Reserves'][i-1]:
    Prod_A = df['Reserves'][i-1]
    else:
        Prod_A = df['Prod'][i-1] * (1 - DeclRate) if i < n else df['Reserves'][i-1]
    Reserves_A = df['Reserves'][i-1] - Prod_A

    df_add['Year'] = [FY]
    df_add['Reserves'] = [Reserves_A]
    df_add['Prod'] = [Prod_A]

df = df.append(df_add, ignore_index=True)
df.round(0).style

Thank you.

Here is the error code I get...

runfile('C:/Users.../TEST.py', wdir='C:/Users...')
Traceback (most recent call last):

  File "<ipython-input-175-365e0e41c561>", line 1, in <module>
    runfile('C:/Users.../TEST.py', wdir='C:/Users...')

  File "C:\ProgramData\Anaconda3\lib\site-packages\spyder\utils\site\sitecustomize.py", line 705, in runfile
    execfile(filename, namespace)

  File "C:\ProgramData\Anaconda3\lib\site-packages\spyder\utils\site\sitecustomize.py", line 102, in execfile
    exec(compile(f.read(), filename, 'exec'), namespace)

  File "C:/Users.../TEST.py", line 22, in <module>
    FY = df['Year'][i-1] + 1

  File "C:\ProgramData\Anaconda3\lib\site-packages\pandas\core\series.py", line 623, in __getitem__
    result = self.index.get_value(self, key)

  File "C:\ProgramData\Anaconda3\lib\site-packages\pandas\core\indexes\base.py", line 2560, in get_value
    tz=getattr(series.dtype, 'tz', None))

  File "pandas/_libs/index.pyx", line 83, in pandas._libs.index.IndexEngine.get_value

  File "pandas/_libs/index.pyx", line 91, in pandas._libs.index.IndexEngine.get_value

  File "pandas/_libs/index.pyx", line 139, in pandas._libs.index.IndexEngine.get_loc

  File "pandas/_libs/hashtable_class_helper.pxi", line 811, in pandas._libs.hashtable.Int64HashTable.get_item

  File "pandas/_libs/hashtable_class_helper.pxi", line 817, in pandas._libs.hashtable.Int64HashTable.get_item

KeyError: -1

Answer 1

You have defined n as follows:

n = 15

You then define a dataframe with one row:

print(df)

   Year  Reserves  Prod
0  2017   442.364  27.8

You then iterate over range(1, 16) :

for i in range(1, n+1):
    FY = df['Year'][i-1] + 1

However, since your dataframe has only one row with index 0 , df['Year'][1] will return with KeyError . This is exactly what you should expect.

You haven't explained what you are trying to achieve. You may wish to do so in a new question . The above explanation describes why you have obtained your error. In general, print is a useful function to determine what is happening at each stage.