Error demonstration

error.py

import peewee
import flask_wtf

from datetime import date, datetime, time

from flask import Flask, request
from flask.ext.sqlalchemy import SQLAlchemy

from flask.ext.admin.contrib.peewee import ModelView
from flask.ext.admin import expose, Admin, AdminIndexView

app = Flask(__name__)
app.config['CSRF_ENABLED'] = True
app.config['SECRET_KEY'] = 'secret'
db = peewee.SqliteDatabase('test_peewee.sqlite', check_same_thread=False)

class BaseModel(peewee.Model):
    class Meta:
        database = db
        
class Model1(BaseModel):
        def __init__(self, test1=None, test2=None, test3=None, test4=None,
                     date_field=None, timeonly_field=None, 
                     datetime_field=None, int_field=None, bool_field=0):
            super(Model1, self).__init__()

            self.test1 = test1
            self.test2 = test2
            self.test3 = test3
            self.test4 = test4
            self.date_field = date_field
            self.timeonly_field = timeonly_field
            self.datetime_field = datetime_field
            self.int_field = int_field
            self.bool_field = bool_field

        test1 = peewee.CharField(max_length=20, null=True)
        test2 = peewee.CharField(max_length=20, null=True)
        test3 = peewee.TextField(null=True)
        test4 = peewee.TextField(null=True)
        date_field = peewee.DateField(null=True)
        timeonly_field = peewee.TimeField(null=True)
        datetime_field = peewee.DateTimeField(null=True)
        int_field = peewee.IntegerField(null=True)
        bool_field = peewee.BooleanField()
        
        def __str__(self):
            return self.test1 # adding "or ''" fixes the issue

class Model2(BaseModel):
    def __init__(self, char_field=None, int_field=None, float_field=None,
                 bool_field=0):
        super(Model2, self).__init__()

        self.char_field = char_field
        self.int_field = int_field
        self.float_field = float_field
        self.bool_field = bool_field
        
    char_field = peewee.CharField(max_length=20)
    int_field = peewee.IntegerField(null=True)
    float_field = peewee.FloatField(null=True)
    bool_field = peewee.BooleanField(null=True)
    
    # Relation
    model1 = peewee.ForeignKeyField(Model1, null=True)


class ModelAdmin(ModelView):
    column_filters = ['datetime_field', 'date_field', 'test1', 'test2', 'test3', 'test4', 'timeonly_field']
    column_editable_list = ['test1', 'test2', 'test3', 'test4', 'int_field', 'timeonly_field', 'date_field', 'datetime_field']
    form_base_class = flask_wtf.Form
    
class Model2Admin(ModelView):
    column_editable_list = ['char_field', 'int_field', 'bool_field', 'enum_field', 'float_field', 'model1']
    

admin = Admin(app, template_mode="bootstrap3")
admin.add_view(ModelAdmin(Model1))
admin.add_view(Model2Admin(Model2))
        
def build_sample_db():
    try:
        Model1.create_table()
    except:
        pass
    try:
        Model2.create_table()
    except:
        pass
            
    Model1('model_bool', bool_field=True).save()
    Model1('model1_obj2',).save()
    Model1(None, test2=u"blah").save() # this causes the issue
    Model1('model1_obj4', test3="blah").save()
    Model1('model1_obj5', test4=u"blah").save()
    Model1('date_obj1', date_field=date(2014,11,17)).save()
    Model1('time_obj1', timeonly_field=time(11,10,9)).save()
    Model1('datetime_obj1', datetime_field=datetime(2014,4,3,1,9,0)).save()
    Model1('int_obj1', int_field=5000).save()
    Model1('int_obj2', int_field=9000).save()
    
    Model2('char_field_val_1', None, None).save()
    Model2('char_field_val_2', None, None).save()
    Model2('char_field_val_3', 5000, 25.9).save()
    Model2('char_field_val_4', 9000, 75.5).save()

if __name__ == '__main__':
    build_sample_db()
    app.run(host="0.0.0.0", port=5001, debug=True)