Summary  
This chapter explains how to import text files into a pandas DataFrame using `pd.read_csv()`, specifying a custom delimiter with `sep` and handling files without header rows by setting `header=None`.  

General domain of usage  
Data analysis

Para leer **archivos de texto** en `pandas`, se puede utilizar la misma función, `pd.read_csv()`. Sin embargo, para asegurar que el archivo de texto se lea correctamente, es fundamental usar un parámetro adicional llamado `sep`, que significa **separador** o **delimitador** en el texto.

```python
# Importing pandas library
import pandas as pd

# Reading a text file into a DataFrame
text_data = pd.read_csv('file.txt', sep='\r', header=None)
```

Si el archivo de texto no contiene una **fila de encabezado** con nombres de columnas, establezca el parámetro `header` en `None`. Esto indica a `pandas` que no debe tratar la primera fila como nombres de columnas.

Para utilizar una nueva línea como separador en un archivo, lo cual es común en archivos de texto, establezca `sep='\r'`. Aquí, `'\r'` representa un retorno de carro, que es un carácter especial utilizado para indicar una nueva línea.

Nota

import unittest
import importlib
import pandas as pd


# Helper function to dynamically generate test names and assertions
def _dynamic_test(test_case, condition, success_message, failure_message):
    if condition:
        test_case._testMethodName = success_message
        test_case.assertTrue(True, success_message)
    else:
        test_case._testMethodName = failure_message
        test_case.fail(failure_message)


def get_first_differing_row(expected_df, actual_df):
    expected_list = expected_df.astype(str).apply(tuple, axis=1)
    actual_list = actual_df.astype(str).apply(tuple, axis=1)

    for i, (row1, row2) in enumerate(zip(expected_list, actual_list)):
        if row1 != row2:
            return i, expected_df.iloc[i].values, actual_df.iloc[i].values

    if len(expected_df) > len(actual_df):
        return len(actual_df), expected_df.iloc[len(actual_df)].values, None
    else:
        return len(expected_df), None, actual_df.iloc[len(expected_df)].values


class TestUserCode(unittest.TestCase):

    def test_text_data_is_declared(self):
        import user_code
        _dynamic_test(
            self,
            hasattr(user_code, 'text_data'),
            "The `text_data` variable is declared.",
            "Expected `text_data` to be declared."
        )

    def test_text_data_is_dataframe(self):
        import user_code

        try:
            condition = isinstance(user_code.text_data, pd.DataFrame)
            failure_message = f"Expected `text_data` to be a `DataFrame`, but got `{type(user_code.text_data).__name__}`."
        except AttributeError:
            condition = False
            failure_message = "The `text_data` variable is not declared."

        _dynamic_test(
            self,
            condition,
            "The variable `text_data` is a `DataFrame`.",
            failure_message
        )

    def test_text_data_is_correct(self):
        import user_code
        row_1 = 'pandas is a software library written for the Python programming language for data manipulation and analysis. In particular, it offers data structures and operations for manipulating numerical tables and time series. It is free software released under the three-clause BSD license.[2] The name is derived from the term "panel data", an econometrics term for data sets that include observations over multiple time periods for the same individuals.[3] Its name is a play on the phrase "Python data analysis" itself.[4] Wes McKinney started building what would become pandas at AQR Capital while he was a researcher there from 2007 to 2010.[5]'
        row_2 = "taken from the site:"
        row_3 = "https://en.wikipedia.org/wiki/Pandas_(software)"
        expected_df = pd.DataFrame([row_1, row_2, row_3])

        variable = 'text_data'
        actual_df = getattr(user_code, variable, None)
        condition = False
        if actual_df is None:
            failure_message = f"The `{variable}` variable is not declared."
        elif not isinstance(actual_df, pd.DataFrame):
            failure_message = f"`{variable}` is not a `DataFrame`."
        elif actual_df.empty:
            failure_message = f"`{variable}` is empty."
        elif actual_df.equals(expected_df):
            condition = True
            failure_message = None
        else:
            idx, expected_row, actual_row = get_first_differing_row(expected_df, actual_df)
            failure_message = f"Expected `{variable}` to contain `{expected_row}` at row {idx}, but got `{actual_row}`."

        _dynamic_test(
            self,
            condition,
            f"`{variable}` contains the correct data.",
            failure_message
        )

    def test_first_row_is_declared(self):
        import user_code
        _dynamic_test(
            self,
            hasattr(user_code, 'first_row'),
            "The `first_row` variable is declared.",
            "Expected `first_row` to be declared."
        )

    def test_first_row_is_series(self):
        import user_code

        try:
            condition = isinstance(user_code.first_row, pd.Series)
            failure_message = f"Expected `first_row` to be a `Series`, but got `{type(user_code.first_row).__name__}`."
        except AttributeError:
            condition = False
            failure_message = "The `first_row` variable is not declared."

        _dynamic_test(
            self,
            condition,
            "The variable `first_row` is a `Series`.",
            failure_message
        )

    def test_first_row_is_correct(self):
        import user_code
        row_1 = 'pandas is a software library written for the Python programming language for data manipulation and analysis. In particular, it offers data structures and operations for manipulating numerical tables and time series. It is free software released under the three-clause BSD license.[2] The name is derived from the term "panel data", an econometrics term for data sets that include observations over multiple time periods for the same individuals.[3] Its name is a play on the phrase "Python data analysis" itself.[4] Wes McKinney started building what would become pandas at AQR Capital while he was a researcher there from 2007 to 2010.[5]'
        row_2 = "taken from the site:"
        row_3 = "https://en.wikipedia.org/wiki/Pandas_(software)"
        expected_df = pd.DataFrame([row_1, row_2, row_3])
        expected_value = expected_df.iloc[0]

        variable = 'first_row'
        actual_value = getattr(user_code, variable, None)
        if actual_value is None:
            condition = False
            failure_message = f"The `{variable}` variable is not declared."
        elif isinstance(actual_value, pd.Series):
            condition = actual_value.equals(expected_value)
            if actual_value.empty:
                failure_message = f"`{variable}` is empty."
            else:
                failure_message = f"Expected `{variable}` to contain `{expected_value.values}`, but got `{actual_value.values}`."
        else:
            condition = False
            failure_message = f"`{variable}` is not a `Series`."

        _dynamic_test(
            self,
            condition,
            f"`first_row` contains the correct values.",
            failure_message
        )


if __name__ == '__main__':
    unittest.main()

test_main.py

Pandas es una biblioteca sumamente intuitiva para el análisis de datos. También está diseñada para manejar grandes conjuntos de datos, utilizando estructuras como DataFrame y Series. Esto la convierte en una herramienta invaluable para la Ciencia de Datos. En esta guía, se presentarán diversas funciones estadísticas, incluyendo cómo encontrar correlaciones, modas, medianas y valores máximos y mínimos dentro de un conjunto de datos. También se abordará el manejo de valores ausentes y la manipulación o eliminación de valores específicos.

Introducción a los fundamentos de la biblioteca pandas. Creación y manipulación de Series y DataFrames, exploración de su estructura y desarrollo de confianza en la realización de operaciones de datos esenciales.

Domine cómo cargar y gestionar datos desde archivos CSV y TXT. Adquiera experiencia práctica importando conjuntos de datos y preparándolos para análisis posteriores utilizando herramientas de pandas.

Aprenda a explorar, limpiar y resumir datos de manera efectiva. Comprenda cómo manejar valores faltantes, extraer información y realizar operaciones estadísticas básicas con pandas.

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