I am trying to create a new variable from a list ('provider') that checks if some ids are present in another column in the data frame:
import pandas as pd
xx = {'provider_id': [1, 2, 30, 8, 8, 7, 9]}
xx = pd.DataFrame(data=xx)
ids = [8,9,30]
names = ["netflix", "prime","sky"]
for id_,name in zip(ids,names):
provider = []
if id_ in xx["provider_id"]:
provider.append(name)
provider
excpected result:
['netflix', 'prime', 'sky']
actual result:
['sky']
So the for
loop keeps overwriting the result of name
inside the loop? This functionality seems weird to me and I honestly don't know how to prevent this other then to write three individual if
statements.
Your loop keeps initialising the list. Move the list outside the loop:
provider = []
for id_,name in zip(ids,names):
if id_ in xx["provider_id"]:
provider.append(name)
print(provider)
One way to make this more efficient is using sets
and isin
to find the matching ids in the dataframe, and then a list comprehension with zip
to keep the corresponding names
.
The error as @quamrana points out is that you keep resetting the list inside the loop.
s = set(xx.loc[xx.isin(ids).values, 'provider_id'].values)
# {8, 9, 30}
[name for id_, name in zip(ids, names) if id_ in s]
# ['netflix', 'prime', 'sky']
Scrap the loops altogether and use the built-in pandas
methods. It will work much faster.
df = pd.DataFrame({'ids': [8,9,30], 'names': ["netflix", "prime","sky"]})
cond = df.ids.isin(xx.provider_id)
df.loc[cond, 'names'].tolist()
['netflix', 'prime', 'sky']
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