AssertionError when use df.loc in python
Question
I created a script to load data, check NA values, and fill all NA values. Here is my code:
import pandas as pd
def filter_df(merged_df, var_list):
ind = merged_df.Name.isin(var_list)
return merged_df[ind]
def pivot_df(df):
return df.pivot(index='Date', columns='Name', values=['Open', 'High', 'Low', 'Close'])
def validation_df(input, summary = False):
df = input.copy()
# na check
missing = df.isna().sum().sort_values(ascending=False)
percent_missing = ((missing / df.isnull().count()) * 100).sort_values(ascending=False)
missing_df = pd.concat([missing, percent_missing], axis=1, keys=['Total', 'Percent'], sort=False)
# fill na
columns = list(missing_df[missing_df['Total'] >= 1].reset_index()['index'])
for col in columns:
null_index = df.index[df[col].isnull() == True].tolist()
null_index.sort()
for ind in null_index:
if ind > 0:
print(df.loc[ind, col])
print(df.loc[ind - 1, col])
df.loc[ind, col] = df.loc[ind - 1, col]
if ind == 0:
df.loc[ind, col] = 0
# outliers check
count = []
for col in df.columns:
count.append(sum(df[col] > df[col].mean() + 2 * df[col].std()) + sum(df[col] < df[col].mean() - 2 * df[col].std()))
outliers_df = pd.DataFrame({'Columns': df.columns, 'Count': count}).sort_values(by = 'Count')
if summary == True:
print('missing value check:/n')
print(missing_df)
print('/n outliers check:/n')
print(outliers_df)
return df
def join_df(price_df, transaction_df, var_list):
price_df = filter_df(price_df, var_list)
price_df = pivot_df(price_df)
joined_df = transaction_df.merge(price_df, how = 'left', on = 'Date')
#joined_df = validation_df(joined_df)
return joined_df
token_path = 'https://raw.githubusercontent.com/Carloszone/Cryptocurrency_Research_project/main/datasets/1_token_df.csv'
transaction_path = 'https://raw.githubusercontent.com/Carloszone/Cryptocurrency_Research_project/main/datasets/transaction_df.csv'
var_list = ['Bitcoin', 'Ethereum', 'Golem', 'Solana']
token_df = pd.read_csv(token_path)
transaction_df = pd.read_csv(transaction_path)
df = join_df(token_df, transaction_df, var_list)
df = validation_df(df)
But it did not work. I checked my code and found this issue came from the loc(). For example:
df = join_df(token_df, transaction_df, var_list)
print(df[df.columns[15]])
print(df.loc[1,df.columns[15]])
what I got is:
0 NaN
1 NaN
2 NaN
3 NaN
4 NaN
..
2250 NaN
2251 NaN
2252 NaN
2253 NaN
2254 NaN
Name: (High, Solana), Length: 2255, dtype: float64
AssertionError Traceback (most recent call last)
<ipython-input-19-75f01cc22c9c> in <module>()
2
3 print(df[df.columns[15]])
----> 4 print(df.loc[1,df.columns[15]])
2 frames
/usr/local/lib/python3.7/dist-packages/pandas/core/indexing.py in __getitem__(self, key)
923 with suppress(KeyError, IndexError):
924 return self.obj._get_value(*key, takeable=self._takeable)
--> 925 return self._getitem_tuple(key)
926 else:
927 # we by definition only have the 0th axis
/usr/local/lib/python3.7/dist-packages/pandas/core/indexing.py in _getitem_tuple(self, tup)
1107 return self._multi_take(tup)
1108
-> 1109 return self._getitem_tuple_same_dim(tup)
1110
1111 def _get_label(self, label, axis: int):
/usr/local/lib/python3.7/dist-packages/pandas/core/indexing.py in _getitem_tuple_same_dim(self, tup)
807 # We should never have retval.ndim < self.ndim, as that should
808 # be handled by the _getitem_lowerdim call above.
--> 809 assert retval.ndim == self.ndim
810
811 return retval
AssertionError:
I don't know why df[column_name] is available, but df.loc[index,columns_name] is wrong.
You can check my code on Colab: https://colab.research.google.com/drive/1Yg280JRwFayW1tdp4OJqTO5-X3dGsItB?usp=sharing
1 answers
solution1
2 ACCPTED
The issue is that you're merging two DataFrames on a column they don't share in common (because you pivoted price_df , Date column became the index). Also the Date columns don't have a uniform format, so you have to make them the same. Replace your join_df function with the one below and it will work as expected.
I added comments on the lines that had to be added.
def join_df(price_df, transaction_df, var_list):
price_df = filter_df(price_df, var_list)
price_df = pivot_df(price_df)
# After pivot the Date column is the index, and price_df has MultiIndex columns
# since we want to merge it with transaction_df, we need to first flatten the columns
price_df.columns = price_df.columns.map('.'.join)
# and reset_index so that we have the index as the Date column
price_df = price_df.reset_index()
# the Dates are formatted differently across the two DataFrames;
# one has the following format: '2016-01-01' and the other '2016/1/1'
# to have a uniform format, we convert the both Date columns to datetime objects
price_df['Date'] = pd.to_datetime(price_df['Date'])
transaction_df['Date'] = pd.to_datetime(transaction_df['Date'])
joined_df = transaction_df.merge(price_df, how = 'left', on = 'Date')
#joined_df = validation_df(joined_df)
return joined_df
Output:
Date total_transaction_count Volume gas_consumption \
0 2016-01-01 2665 NaN NaN
1 2016-01-02 4217 NaN NaN
2 2016-01-03 4396 NaN NaN
3 2016-01-04 4776 NaN NaN
4 2016-01-05 26649 NaN NaN
... ... ... ... ...
2250 2022-02-28 1980533 1.968686e+06 8.626201e+11
2251 2022-03-01 2013145 2.194055e+06 1.112079e+12
2252 2022-03-02 1987934 2.473327e+06 1.167615e+12
2253 2022-03-03 1973190 3.093248e+06 1.260826e+12
2254 2022-03-04 1861286 4.446204e+06 1.045814e+12
old_ave_gas_fee new_avg_gas_fee new_avg_base_fee \
0 0.000000e+00 0.000000e+00 0.000000e+00
1 0.000000e+00 0.000000e+00 0.000000e+00
2 0.000000e+00 0.000000e+00 0.000000e+00
3 0.000000e+00 0.000000e+00 0.000000e+00
4 0.000000e+00 0.000000e+00 0.000000e+00
... ... ... ...
2250 6.356288e-08 6.356288e-08 5.941877e-08
2251 5.368574e-08 5.368574e-08 4.982823e-08
2252 5.567472e-08 5.567472e-08 4.782055e-08
2253 4.763823e-08 4.763823e-08 4.140883e-08
2254 4.566440e-08 4.566440e-08 3.547666e-08
new_avg_priority_fee Open.Bitcoin Open.Ethereum ... High.Golem \
0 0.000000e+00 430.0 NaN ... NaN
1 0.000000e+00 434.0 NaN ... NaN
2 0.000000e+00 433.7 NaN ... NaN
3 0.000000e+00 430.7 NaN ... NaN
4 0.000000e+00 433.3 NaN ... NaN
... ... ... ... ... ...
2250 4.144109e-09 37707.2 2616.34 ... 0.48904
2251 3.857517e-09 43187.2 2922.44 ... 0.48222
2252 7.854179e-09 44420.3 2975.80 ... 0.47550
2253 6.229401e-09 NaN NaN ... NaN
2254 1.018774e-08 NaN NaN ... NaN
High.Solana Low.Bitcoin Low.Ethereum Low.Golem Low.Solana \
0 NaN 425.9 NaN NaN NaN
1 NaN 430.7 NaN NaN NaN
2 NaN 423.1 NaN NaN NaN
3 NaN 428.6 NaN NaN NaN
4 NaN 428.9 NaN NaN NaN
... ... ... ... ... ...
2250 NaN 37458.9 2574.12 0.41179 NaN
2251 NaN 42876.6 2858.54 0.45093 NaN
2252 NaN 43361.3 2914.70 0.43135 NaN
2253 NaN NaN NaN NaN NaN
2254 NaN NaN NaN NaN NaN
Close.Bitcoin Close.Ethereum Close.Golem Close.Solana
0 434.0 NaN NaN NaN
1 433.7 NaN NaN NaN
2 430.7 NaN NaN NaN
3 433.3 NaN NaN NaN
4 431.2 NaN NaN NaN
... ... ... ... ...
2250 43188.2 2922.50 0.47748 NaN
2251 44420.3 2975.81 0.47447 NaN
2252 43853.2 2952.47 0.43964 NaN
2253 NaN NaN NaN NaN
2254 NaN NaN NaN NaN
[2255 rows x 24 columns]
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.
Related Question
Python df.loc with regex
How to use df.loc and if condtions in python pandas to delete a row
Python change NaN value with df.loc
loop under df.loc in python dataframe
Python df.loc not working for variables
SettingWithCopyWarning message in Pandas/Python with df.loc
Using df.loc[] and In
Python and pandas: is df[“colName”] exactly equivalent to df.loc[:,“colName”]?
Values are missing when using df.loc after changing the index in python-pandas
Get df.loc['column_name'] when column_name is a variable in Python Pandas
Related Tags