How to update values in Python's dictionary?

April 23, 2022

My dictionary looks like below, and I am following this link to update the values in "Column_Type" key. Bascially, I would like to replace values "String" with "VARCHAR(256)", DATE with "NUMBER (4,0)", Int with "NUMBER" and Numeric with "Number". Whenever I run below code, my values are not getting updated to my dictionary.My desired output for updated dictionary is as below

Please note: The location of column_types might vary as well. For ex: Column_type[String] currently is at position 1, but It might be at position 3 later on .

{'Column_name': ['Name', 'Salary', 'Date', 'Phone'], 'Column_Type': ['String', 'Numeric', 'Date', 'Int']}

Code:

for key1, key2 in my_dict.items():
    if key2== 'String':
        my_dict[key2] = "VARCHAR(256)"
print(my_dict)

Desired Output:

{'Column_name': ['Name', 'Salary', 'Date', 'Phone'], 'Column_Type': ['VARCHAR(256)', 'NUMBER', 'NUMBER(4,0)', 'NUMBER']}

>Solution :

In your example, your keys are "Column_Name" and Column_Type". There is no key named "String" in your dict. Both values in your dict are of type list so neither are equal to the string String either.

What you want is to replace a specific value in a list.

Try like this:

for index, value in enumerate(my_dict["Column_Type"]):
    if value == "String":
        my_dict["Column_Type"][index] = "VARCHAR(256)"

This replaces the value in the list, not the dict. That is what you want.

If you need to replace multiple values you can use a dict, like @Jeremy suggested:

type_strs = {
    'String': 'VARCHAR(256)',
    'Numeric': 'NUMBER',
    'Date': 'NUMBER(4,0)',
    'Int': 'NUMBER'
}

for index, value in enumerate(my_dict["Column_Type"]):
    my_dict["Column_Type"][index] = type_strs.get(value, value)

Here, the .get() function on a dict returns the value corresponding to the key given by the first argument, or the second argument if no such key exists.