DataFrame operations didn't change orginal

[HoldYourBreath]

hi, i just want to fully understand dataframe operations. i read some documantations. but i have some questions

1)i want to change my dataframe. not to copy one. it is ok in the beginning but in later line somehow it changes automaticly.

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import pandas as pd import numpy as np import matplotlib.pyplot as plt import seaborn as sbn   DF=pd.read_excel("merc.xlsx") DF=DF.sort_values("price",ascending=False).iloc[131:] price=DF.iloc[:,1:2]   from sklearn import preprocessing ohe = preprocessing.OneHotEncoder() le=preprocessing.LabelEncoder() trans=DF.iloc[:,2:3].values trans[:,0]=le.fit_transform(DF.iloc[:,2]) trans = ohe.fit_transform(trans).toarray() trans=pd.DataFrame(data=trans, index=range(len(trans)), columns=["Auto","man","other","semi"]) DF=DF.drop("price", axis=1) DF=DF.drop("transmission",axis=1)   DF=pd.concat([DF,trans],axis=1)   from sklearn.model_selection import train_test_split x_train, x_test, y_train, y_test=train_test_split (DF,price, test_size=0.33, random_state=15)   from sklearn.preprocessing import MinMaxScaler scaler = MinMaxScaler() scaler.fit(x_train) x_train = scaler.transform(x_train) x_test = scaler.transform (x_test)

T

Error:
raceback (most recent call last):

  File "C:\Users\oby_pc\Desktop\programing\veri bilimi için python ve tensorflow\2_merc.py", line 30, in <module>
    x_train, x_test, y_train, y_test=train_test_split (DF2,price, test_size=0.33, random_state=15)

  File "C:\Users\oby_pc\anaconda3\lib\site-packages\sklearn\model_selection\_split.py", line 2127, in train_test_split
    arrays = indexable(*arrays)

  File "C:\Users\oby_pc\anaconda3\lib\site-packages\sklearn\utils\validation.py", line 293, in indexable
    check_consistent_length(*result)

  File "C:\Users\oby_pc\anaconda3\lib\site-packages\sklearn\utils\validation.py", line 256, in check_consistent_length
    raise ValueError("Found input variables with inconsistent numbers of"

ValueError: Found input variables with inconsistent numbers of samples: [13116, 12988]

i understand the error but i didnt understand why it happens?

2) when i create new DF with DF2 the error is same

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import pandas as pd import numpy as np import matplotlib.pyplot as plt import seaborn as sbn   DF=pd.read_excel("merc.xlsx") DF2=DF.sort_values("price",ascending=False).iloc[131:] price=DF2.iloc[:,1:2]   from sklearn import preprocessing ohe = preprocessing.OneHotEncoder() le=preprocessing.LabelEncoder() trans=DF2.iloc[:,2:3].values trans[:,0]=le.fit_transform(DF2.iloc[:,2]) trans = ohe.fit_transform(trans).toarray() trans=pd.DataFrame(data=trans, index=range(len(trans)), columns=["Auto","man","other","semi"]) DF2=DF2.drop("price", axis=1) DF2=DF2.drop("transmission",axis=1)   DF2=pd.concat([DF2,trans],axis=1)   from sklearn.model_selection import train_test_split x_train, x_test, y_train, y_test=train_test_split (DF2,price, test_size=0.33, random_state=15)   from sklearn.preprocessing import MinMaxScaler scaler = MinMaxScaler() scaler.fit(x_train) x_train = scaler.transform(x_train) x_test = scaler.transform (x_test)

bonus question : is there any easier way to use ohe and le than my codes?

tahnk you

buran write Jan-10-2021, 02:19 PM:
Please, use proper tags when post code, traceback, output, etc. This time I have added tags for you.
See BBcode help for more info.

[jefsummers]

It would help to have the whole error message, so we can see where this is happening.

I believe the issue is the way Python handles variable names. a=b does not copy b to a, rather it creates variable a that points to the same value that b does. Changes to that value mean that a and b are both changed. Usually. Unless the operation results in a reassignment that separates the two.

Sounds confusing, would refer you to a Pycon talk by Ned Batchelder PyCon 2015

[jefsummers]

Add:

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a = [1,2,3] b = a b.append(4) print(a)

Output:
[1, 2, 3, 4]

Appended to b but it affected a as well.

[HoldYourBreath]

It would help to have the whole error message, so we can see where this is happening.

I believe the issue is the way Python handles variable names. a=b does not copy b to a, rather it creates variable a that points to the same value that b does. Changes to that value mean that a and b are both changed. Usually. Unless the operation results in a reassignment that separates the two.

Sounds confusing, would refer you to a Pycon talk by Ned Batchelder PyCon 2015

edited orginal massage and add whole error massage

i understand change issue. but in my example it didnt change. i trace step by step DF.shape and after "line 22" it change to its orginal value so the alterations that i make is gone.

[HoldYourBreath]

Add:

1 2 3 4

a = [1,2,3] b = a b.append(4) print(a)

Output:
[1, 2, 3, 4]

Appended to b but it affected a as well.

i understand this. but in my example some how in some where a changes its orginal values like [1,2,3] again

[jefsummers]

The difference is 128 records. Would check the length of DF and price right before the error. BTW - error message says line 30 but you don't give us line 30. I am assuming the error is actually occurring in line 24.