pandas: REGR: invalid cache after take operation with non-consolidated dataframe

a program run ok with pandas 1.0.5, but after upgrade to 1.1.0. it fail. i found sometimes when I change one cell of dataframe value, print(df) and it doesn’t change. but i use ==, it says changed. for example: original cell value is A, then i change cell value to B. A=B print df, it show still A df.at(x, x) == B, it says TRUE.

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MarcoGorelli’s edit: here’s a reproducible example:

import pandas as pd


position = pd.DataFrame(columns=["code", "startdate"])
position = position.append([{"code": "a", "startdate": 0}])

# These two lines should not change anything.
# BUT, commenting either of them out makes this code run as intendeed
position["code"] == "A"
position[position["startdate"] == 0]

position.at[0, "code"] = "A"

print(position.at[0, "code"])
print(position)

output:

A
  code startdate
0    a         0

expected output:

A
  code startdate
0    A         0