python assign value of dataframe by conditions

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description: python assign or set value if conditions match

python assign or set value based on conditions

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import pandas

data = pandas.DataFrame({"test": [10, 20, 30, 40], "a": [1, 1, 1, 2], "b": [0, 2, 2, 2]})
# test  a  b
# 0    10  1  0
# 1    20  1  2
# 2    30  1  2
# 3    40  2  2

filter the data with condtion 1

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tmp = data[data["a"] == 1]
# test  a  b
# 0    10  1  0
# 1    20  1  2
# 2    30  1  2

filter the data with condition 2

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tmp = tmp[tmp["b"] == 2]
# test  a  b
# 1    20  1  2
# 2    30  1  2

get the index of the data

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indexes = tmp.index
# Int64Index([1, 2], dtype='int64')

change values by indexes and column name

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data._set_value(indexes, 'test', 888888)
# test  a  b
# 0      10  1  0
# 1  888888  1  2
# 2  888888  1  2
# 3      40  2  2

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