pandas中set_index与reset_index

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import pandas as pd

# 创建示例
data = {
    "a": ["bar", "bar", "foo", "foo"],
    "b": ["one", "two", "one", "two"],
    "c": ["z", "y", "x", "w"],
    "d": [1.0, 2.0, 3.0, 4.0]
}
df = pd.DataFrame(data=data)
# print(df)
#      a    b  c    d
# 0  bar  one  z  1.0
# 1  bar  two  y  2.0
# 2  foo  one  x  3.0
# 3  foo  two  w  4.0


# set_index 创建索引
indexed1 = df.set_index("c")
# print(indexed1)
#      a    b    d
# c
# z  bar  one  1.0
# y  bar  two  2.0
# x  foo  one  3.0
# w  foo  two  4.0

indexed2 = df.set_index(["a", "b"])
# print(indexed2)
#          c    d
# a   b
# bar one  z  1.0
#     two  y  2.0
# foo one  x  3.0
#     two  w  4.0


# reset_index 还原索引 变为默认的整型索引
res2 = indexed2.reset_index()

# print(res2)
#      a    b  c    d
# 0  bar  one  z  1.0
# 1  bar  two  y  2.0
# 2  foo  one  x  3.0
# 3  foo  two  w  4.0