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Articles on Trending Technologies
Technical articles with clear explanations and examples
Node.js – util.debuglog() Method
The util.debuglog() method creates a function that can be used to write the desired error/debug messages to stderr. These error messages are written only upon the existence of the NODE_DEBUG environment variable.Syntaxutil.debuglog(section, [callback])ParametersThe parameters are described below −section − This parameter takes the portion of the application for which the debug log is being created.callback − This is the callback function which will receive the pointer if any error occurs during the execution of method.Example 1Create a file with the name "debuglog.js" and copy the following code snippet -// util.debuglog() demo example // Importing the util module const util ...
Read MoreHow to get the list of column headers from a Pandas DataFrame?
To get a list of Pandas DataFrame column headers, we can use df.columns.values.StepsCreate a two-dimensional, size-mutable, potentially heterogeneous tabular data, df.Print the input DataFrame.Print the list of df.columns.values output.Exampleimport pandas as pd df = pd.DataFrame( { "x": [5, 2, 1, 9], "y": [4, 1, 5, 10], "z": [4, 1, 5, 0] } ) print "Input DataFrame is:", df print "List of headers are: ", list(df.columns.values)OutputInput DataFrame is: x y z 0 5 4 4 1 2 1 1 2 1 5 5 3 9 10 0 List of headers are: ['x', 'y', 'z']
Read MoreHow to change the order of Pandas DataFrame columns?
To change the order of DataFrame columns, we can take the following Steps −StepsMake two-dimensional, size-mutable, potentially heterogeneous tabular data, df.Print the input DataFrame.Get the list of DataFrame columns, using df.columns.tolist()Change the order of DataFrame columns.Modify the order of columns of the DataFrame.Print the DataFrame after changing the columns order.Exampleimport pandas as pd df = pd.DataFrame( { "x": [5, 2, 1, 9], "y": [4, 1, 5, 10], "z": [4, 1, 5, 0] } ) print "Input DataFrame is:", df cols = df.columns.tolist() cols = cols[-1:] + cols[:-1] ...
Read MoreCreate a Pandas Dataframe by appending one row at a time
To create a Pandas DataFrame by appending one row at a time, we can iterate in a range and add multiple columns data in it.StepsCreate a two-dimensional, size-mutable, potentially heterogeneous tabular data, df.Print the input DataFrame.Iterate in a range of 10.Assign values at different index with numbers.Print the created DataFrame.Exampleimport pandas as pd import random df = pd.DataFrame( { "x": [], "y": [], "z": [] } ) print "Input DataFrame:", df for i in range(10): df.loc[i] = [i, random.randint(1, 10), random.randint(1, 10)] print "After appending ...
Read MoreHow are iloc and loc different in Python Pandas?
Let's take an example to understand the difference between iloc and loc. Basically loc[0] returns the value present at 0 index, whereas iloc[0] returns the value present at the first location of a series.StepsCreate a one-dimensional ndarray with axis labels (including time series).Print the input series.Use loc[0] to print the value present at 0th index.Use iloc[0] to print the value present at the first location of the series table.Exampleimport pandas as pd s = pd.Series(list("AEIOU"), index=[2, 1, 0, 5, 8]) print "Input series is:", s print "Value at index=0:", s.loc[0] print "Value at the 1st location of the series:", s.iloc[0]OutputInput ...
Read MoreDeleting a DataFrame row in Python Pandas based on column value
To delete a DataFrame row in Pandas based on column value, we can take the following Steps −StepsCreate a two-dimensional, size-mutable, potentially heterogeneous tabular data, df.Print the input DataFrame.Here, we will delete the row from the DataFrame that contains 0 in its Z-column, using df=df[df.z != 0]Print the updated DataFrame, after deleting row based on column value.Exampleimport pandas as pd df = pd.DataFrame( { "x": [5, 2, 1, 9], "y": [4, 1, 5, 10], "z": [4, 1, 5, 0] } ) print "Input DataFrame is:", df df = ...
Read MoreHow to count the NaN values in a column in a Python Pandas DataFrame?
To count the NaN values in a column in a Pandas DataFrame, we can use the isna() method with sum.StepsCreate a series, s, one-dimensional ndarray with axis labels (including time series).Print the series, s.Count the number of NaN present in the series.Create a two-dimensional, size-mutable, potentially heterogeneous tabular data, df.Print the input DataFrame.Find NaN count column wise.Print the count DataFrame.Exampleimport pandas as pd import numpy as np s = pd.Series([1, np.nan, 3, np.nan, 3, np.nan, 7, np.nan, 3]) print "Input series is:", s count = s.isna().sum() print "NAN count in series: ", count df = pd.DataFrame( { ...
Read MoreConvert a Pandas DataFrame to a NumPy array
To convert a Pandas DataFrame to a NumPy array, we can use to_numpy().StepsCreate a two-dimensional, size-mutable, potentially heterogeneous tabular data, df.Print the input DataFrame.Print the NumPy array of the given array, using df.to_numpy().Print the NumPy array of the given array for a specific column, using df['x'].to_numpy().Exampleimport pandas as pd df = pd.DataFrame( { "x": [5, 2, 1, 9], "y": [4, 1, 5, 10], "z": [4, 1, 5, 0] } ) print "Input DataFrame is:", df print "DataFrame to numpy is:", df.to_numpy() print "DataFrame to numpy is:", df['x'].to_numpy()OutputInput DataFrame ...
Read MoreHow to make a multi-index in Pandas?
To make a multi-index in Pandas, we can use groupby with list of columns.StepsCreate a two-dimensional, size-mutable, potentially heterogeneous tabular data, df.Print the input DataFrame.Print the index of DataFrame count.Use groupby to get different levels of a hierarchical index and count it.Print the mulitindex set in step 4.Exampleimport pandas as pd df = pd.DataFrame( { "x": [5, 2, 1, 9], "y": [4, 1, 5, 10], "z": [4, 1, 5, 0] } ) print "Input DataFrame is:", df print "Default index: ", df.count().index df1 = df.groupby(["x", "y"]).count() print ...
Read MoreHow to reset hierarchical index in Pandas?
To reset hierarchical index in Pandas, we can use reset_index() method.StepsCreate a two-dimensional, size-mutable, potentially heterogeneous tabular data, df.Print the input DataFrame.Use groupby to get different levels of a hierarchical index and count it.Print multi-hierarchical index DataFrame.Reset the multi-hierarchical index DataFrame, using df.reset_index().Print the new updated DataFrame.Exampleimport pandas as pd df = pd.DataFrame({"x": [5, 2, 1, 9], "y": [4, 1, 5, 10]}) print "Input DataFrame is:", df df1 = df.groupby(["x", "y"]).count() print "Hierarchical Index of input DataFrame is:", df1 df2 = df1.reset_index() print "After resetting: ", df2OutputInput DataFrame is: x y 0 5 4 ...
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