Adding a column of list to a dataframe python

Question

I have a data frame in pandas as below:

    Type      Rand      Arrival
     0         0.3        4
     2         0.64       3
     1         0.98       12

Now, I want to add a new column to it that is list in each row:

    Type      Rand      Arrival         Park
     0         0.3        4          [5,10,15,20]
     2         0.64       3          [4,9,14,19]
     1         0.98       12         [6,11,16,21]

I want to do that based on the 'Rand' column by comparing it to some values using the following commands:

   df.loc[ (df.Rand <= 0.4) , 'Park' ] = [5,10,15,20]
   df.loc[ (df.Rand > 0.4) & (df.Rand <= 0.8) , 'Park' ] = [4,9,14,19]
   df.loc[ (df.Rand > 0.8) , 'Park' ] = [6,11,16,21]

But I am getting the following error:

  Must have equal len keys and value when setting with an iterable.

Could you please tell me hot to overcome this issue?

Community · Accepted Answer · 2017-05-23 12:16:36Z

2

>>> df.loc[df.Rand <= 0.4, 'Park'] = pd.Series([[5, 10, 15, 20]], index=df.index)
>>> df.loc[(df.Rand > 0.4) & (df.Rand <= 0.8), 'Park'] = pd.Series([[4,9,14,19]], index=df.index)
>>> df.loc[(df.Rand > 0.8), 'Park'] = pd.Series([[6,11,16,21]], index=df.index)
>>> df
   Type  Rand  Arrival             Park
0     0  0.30        4  [5, 10, 15, 20]
1     2  0.64        3   [4, 9, 14, 19]
2     1  0.98       12  [6, 11, 16, 21]

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edited May 23, 2017 at 12:16

CommunityBot

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answered Nov 2, 2016 at 17:36

Dennis Golomazov

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spiderface · Accepted Answer · 2016-11-02 17:40:12Z

1

df.loc[ (df.Rand <= 0.4) , 'Park' ] = lambda:[5,10,15,20]
df.loc[ (df.Rand > 0.4) & (df.Rand <= 0.8) , 'Park' ] = lambda:[4,9,14,19]
df.loc[ (df.Rand > 0.8) , 'Park' ] = lambda:[6,11,16,21]

df.Park = df.Park.apply(lambda x: x())

answered Nov 2, 2016 at 17:40

spiderface

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