CODEWITHSUNDEEP
pythonpandasdictionarydataframeiteration
magladde
magladde

Reputation: 634

Iterating over a data frame, creating a dictionary based on values

I am trying to iterate through a dataframe in pandas and generate a dictionary based off of the values in a column. I am interested in capturing the column name every time the value in the column is equal to a value of 3. Given a dataframe below:

Sample         Variable 1    Variable 2    Variable 3
Sample 1          1                3             1
Sample 2          3                0             3
Sample 3          3                3             3
Sample 4          2                1             3

I am interested in creating a dictionary that gives me:

{'Sample 1': [Variable 2], 'Sample 2': [Variable 1, Variable3], 'Sample 3': [Variable 1, Variable 2, Variable 3], 'Sample 4': [Variable3]}

Upvotes: 2

Views: 4804

Answers (2)

vielkind
vielkind

Reputation: 2980

You can do this by converting your DataFrame into a dict and then apply dictionary comprehension to get a list of the variables equal to 3.

df_dict = df.to_dict(orient="index")
{k: [k1 for (k1, v1) in v.items() if v1 == 3] for (k, v) in df_dict.items()}

Upvotes: 4

user3483203
user3483203

Reputation: 51185

Setup

df = pd.DataFrame({'Sample': ['Sample 1', 'Sample 2', 'Sample 3', 'Sample 4'], 'Variable 1': [1,3,3,2], 'Variable 2': [3,0,3,1], 'Variable 3': [1,3,3,3]})

set_index with unstack:

s = df.set_index('Sample').unstack().reset_index()

Then groupby and apply, and finally to_dict:

s[s[0].eq(3)].groupby('Sample')['level_0'].apply(list).to_dict()

{'Sample 1': ['Variable 2'],
 'Sample 2': ['Variable 1', 'Variable 3'],
 'Sample 3': ['Variable 1', 'Variable 2', 'Variable 3'],
 'Sample 4': ['Variable 3']}

Upvotes: 2

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