add_columns.py

#!/usr/bin/env python
"""
    Example that demonstrates several ways of defining your own columns.
"""
from __future__ import print_function

import sys, logging
from math import sqrt

from qtpy.QtCore import Qt

from objbrowser import browse
from objbrowser.utils import logging_basic_config
from objbrowser.attribute_model import (AttributeModel, 
                                        DEFAULT_ATTR_COLS, DEFAULT_ATTR_DETAILS,  
                                        safe_tio_call, safe_data_fn)

logger = logging.getLogger(__name__)

   
def safe_tio_sqrt(tree_item):
    """ Calls math.sqrt(tree_item.obj) and converts the result to a string. 
        Returns empty string in case the sqrt cannot be calculated.
    """ 
    tio = tree_item.obj
    try:
        return str(sqrt(tio))
    except Exception:
        return ""
    
        
def my_browse(*args, **kwargs):
    """ Creates and starts an ObjectBrowser with added sqrt columns.
    """
    doc_str = "The sqrt of an object if it can be calculated"
    width = 120 # pixels
    
    # 1: The data_fn should be a TreeItem to string (or unicode) function. If you have 
    #    a function with one input and one output parameter (e.g. the sqrt function), 
    #    you must wrap it with a lambda expression like this.
    sqrt_attr_model_1 = AttributeModel('sqrt 1', 
        doc         = doc_str, 
        data_fn     = lambda tree_item: str(sqrt(tree_item.obj)),
        col_visible = True,
        width       = width,   
        alignment   = Qt.AlignRight) 

    # 2) Example 1 above displays an error message in the cell in case of an exception.
    #    To prevent this, you can use the safe_tio_call that that returns an empty  
    #    string in case of an exception.
    sqrt_attr_model_2 = AttributeModel('sqrt 2', 
        doc         = doc_str, 
        data_fn     = lambda tree_item: safe_tio_call(sqrt, tree_item),
        col_visible = True,
        width       = width,   
        alignment   = Qt.AlignRight) 
    
    # 3) Of course you can also write a wrapper function yourself.
    sqrt_attr_model_3 = AttributeModel('sqrt 3', 
        doc         = doc_str, 
        data_fn     = safe_tio_sqrt,
        col_visible = True,
        width       = width,   
        alignment   = Qt.AlignRight) 

    # 4) The simplest solution is to use the safe_data_fn function which creates the
    #    wrapped function.
    sqrt_attr_model_4 = AttributeModel('sqrt 4', 
        doc         = doc_str, 
        data_fn     = safe_data_fn(sqrt),
        col_visible = True,
        width       = width,   
        alignment   = Qt.AlignRight) 

    attribute_columns = list(DEFAULT_ATTR_COLS)
    attribute_columns.insert(5, sqrt_attr_model_1)
    attribute_columns.insert(6, sqrt_attr_model_2)
    attribute_columns.insert(7, sqrt_attr_model_3)
    attribute_columns.insert(8, sqrt_attr_model_4)
    
    # You can also add the attribute to the details pane
    attribute_details = list(DEFAULT_ATTR_DETAILS)
    attribute_details.insert(0, sqrt_attr_model_1)
    
    return browse(*args, 
                  attribute_columns = attribute_columns,
                  attribute_details = attribute_details,  
                  **kwargs)
    
  
def main():
    """ Main program 
    """
    logging_basic_config('DEBUG')
    logger.info('Started example')

    # define some local variables
    lst = range(-5, 5) 
    b = True
    i = 555 
    f = 6.2 
    c = 3.2j - 0.1
    m = -4
    n = None
    s = '44'
    z = 'zonk'
            
    exit_code = my_browse(locals(),  
                          show_callable_attributes=False,
                          show_dunder_attributes=False)

    logging.info('Done example')
    sys.exit(exit_code)

if __name__ == '__main__':
    main()