Snippets
indexing

How-to articles, tricks, and solutions about INDEXING

file upload php $_FILES undefined index error

The error "Undefined index: (name of the file input)" in PHP usually occurs when the form that is used to upload the file is not properly configured.

php file undefined upload indexing

Finding the index of an item in a list

To find the index of an item in a list in Python, you can use the index() method of the list.

list python indexing

Get first row value of a given column

Here's an example of how you can get the first row value of a given column in a Pandas DataFrame in Python:

python indexing pandas head

How are iloc and loc different?

iloc and loc are both used to select rows and columns from a Pandas DataFrame, but they work differently.

python indexing pandas dataframe pandas-loc

How can I employ "if exists" for creating or dropping an index in MySQL?

In MySQL, you can use the "IF EXISTS" clause when creating or dropping an index to prevent an error from occurring if the index does not exist.

php MySQL indexing

How do I get the last element of a list?

To get the last element of a list, you can use negative indexing.

list python indexing

How do you reindex an array in PHP but with indexes starting from 1?

You can use the array_values function to get a new array with the values of the original array, and then use the array_combine function to create an array using the new values and an indexed array of keys starting from 1:

php arrays indexing

How to convert index of a pandas dataframe into a column

To convert the index of a pandas DataFrame into a column, you can use the reset_index() function, and specify that you want to move the index to a new column with the inplace=True and name parameter.

python indexing pandas dataframe series

How to find the index of an element in an int array?

To find the index of an element in an int array in Java, you can use the indexOf() method of the Arrays class.

java arrays search indexing

How to remove an element from a list by index

To remove an element from a list by index in Python, you can use the pop() method.

list python indexing

Python Pandas: Get index of rows where column matches certain value

You can use the .loc method to filter the DataFrame and get the boolean mask, and then use the .index property to get the index of the rows that match the certain value.

python indexing pandas dataframe

Replace a character at a specific index in a string?

To replace a character at a specific index in a string in Java, you can use the substring() method of the java.lang.

java string character replace indexing

Selecting a row of pandas series/dataframe by integer index

You can use the .iloc[] property to select a row by its integer index in a pandas DataFrame or Series.

python indexing pandas dataframe