python - Please tell this newbie what the difference is between these two list outputs? -


i struggling , have tracked down difference between 2 lists inside code: python debugger:

(pdb) values ['thing1', 'thing2', 'thing3'] (pdb) values2 [['thing1', 'thing2', 'thing3']]

i do not want double brackets, mean , how rid of them?

'values' creation by: values = ['thing1','thing2','thing3']

'values2' creation by:

for report in report.objects.filter(id=id):         values2.append([str(report.name), str(report.subject), str(report.description)])

why getting difference , how can values2 values ?

don't think of "double brackets". think of 2 sets of single brackets, 1 inside other. set of brackets means have list. 2 sets of single brackets means have 2 lists. 1 set of single brackets inside means have list inside list.

this because value appended list, because did values2.append([...]). [...] list, appended list; is, put nested list inside values2.

if don't want that, do:

values2.extend([str(report.name), str(report.subject), str(report.description)])

extend add each element of list separate element, instead of adding whole list 1 element. (whether work in larger context of program depends on values2.)


Comments

Post a Comment

Popular posts from this blog

Python Kivy ListView: How to delete selected ListItemButton? -

Image
i'm trying learn kivy building simple todo-list app suggested dusty phillips, author of book "creating apps in kivy". this code far: from kivy.app import app kivy.uix.boxlayout import boxlayout kivy.properties import objectproperty kivy.uix.listview import listitembutton class taskbutton(listitembutton): pass class todoroot(boxlayout): task_input = objectproperty() task_list = objectproperty() def add_task(self): self.task_list.adapter.data.extend([self.task_input.text]) self.task_list._trigger_reset_populate() def del_task(self): pass class todoapp(app): def build(self): return todoroot() if __name__ == '__main__': todoapp().run() and kv file: #: import main todo #: import listadapter kivy.adapters.listadapter.listadapter #: import listitembutton kivy.uix.listview.listitembutton todoroot: <todoroot>: orientation: "vertical" task_input: task_input_view t...
Read more

ruby - How do I merge two hashes into a hash of arrays? -

http://codepad.org/wmyzqlis i'd merge these 2 arrays: a = { :a => 'a', :b => 'b', :d => 'd' } b = { :a => '1', :b => 'b', :c => 'c' } into hash looks this: {:a => ["a", "1"], :b => ["b", "b"], :c => [nil, "c"], :d => ["d", nil] } this doesn't work: p a.merge(b) { |k, v1, v2| [v1, v2] } # {:c=>"c", :a=>["a", "1"], :b=>["b", "b"], :d=>"d"} it's because hash#merge call block duplicate keys. a = { :a => 'a', :b => 'b', :d => 'd' } b = { :a => '1', :b => 'b', :c => 'c' } hash[(a.keys|b.keys).map { |key| [key, [a.fetch(key, nil), b.fetch(key, nil)]] }] # => {:a=>["a", "1"], :b=>["b", "b"], :d=>["d", nil], :c=>...
Read more