CODEWITHSUNDEEP
pythonpandas
Javide
Javide

Reputation: 2657

ValueError: The truth value of a Series is ambiguous on creation of new column

Using assign in Pandas 1.0 I would like to create a new flag column based on the following logic:

import numpy as np
import pandas as pd

df = pd.DataFrame({'val': [10, 2, 0, 1, 0.4, 2]})
df = df.assign(
    flag=lambda x: False if np.bool(x['val'] == 0) else True if np.bool(x['val'] < 0.5) else False
)

I expect:

df
   val    flag
0   10    False
1    2    False
2    0    False
3    1    False
4    0.4  True
5    2    False

Instead I get:

ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all()

I tried with np.where(), np.any(), np.all() but I do not get the expected result.

Upvotes: 1

Views: 152

Answers (1)

jezrael
jezrael

Reputation: 863751

Chain condition by & for bitwise AND:

df = pd.DataFrame({'val': [10, 2, 0, 1, 0.4, 2]})

df = df.assign(flag= (df['val'] < 0.5) & (df['val'] != 0))

If val is count by some chained method is necessary lambda:

df = df.assign(flag=lambda x: (x['val'] < 0.5) & (x['val'] != 0))
print (df)
    val   flag
0  10.0  False
1   2.0  False
2   0.0  False
3   1.0  False
4   0.4   True
5   2.0  False

Upvotes: 2

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