Flatten list sublists

[chesschaser]

Hi guys! I have this list:

1	mylist = ["Hello", ["Hello2", "Hello3"], "Hello4"]

However, I want the list to be this instead (don't say just remove the sublist. This is not the real list. Just a test list. The real list comes from a function return so that wouldn't work):

1	mylist = ["Hello", "Hello2", "Hello3", "Hello4"]

I have tried this:

1	sum(map(str.split, sum([[k] if isinstance(k, str) else k for k in single_list1], [])), [])

However this will not work as the real list has spaces and this splits them into different list items too which I do not want.
I have tried a number of different functions in place of str.split however none worked.

Please help

[snippsat]

That line is easy to read
This approach is usually what i have used for this,can also trow in a yield from(new in Python 3.3) to make it a little cooler.

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def flatten(seq):     for item in seq:         if isinstance(item, list):             yield from flatten(item)         else:             yield item   mylist = ["Hello", ["Hello2", "Hello3"], "Hello4"] print(list(flatten(mylist)))

Output:
['Hello', 'Hello2', 'Hello3', 'Hello4']

[chesschaser]

Ok. I'll try it

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It doesn't work. In my real code, the Listbox has some silly object code.
Unless I try this ...
Hang on

[DeaD_EyE]

Non-Recursive implementation with a stack:

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from collections import deque     def flatten(iterable):     stack = deque(iterable)     while stack:         item = stack.popleft()         if isinstance(item, list):             stack.extendleft(item)         else:             yield item     mylist = ["Hello", ["Hello2", "Hello3"], "Hello4"] flatten_list = list(flatten(mylist)) print(flatten_list)

Output:
['Hello', 'Hello3', 'Hello2', 'Hello4']

The isinstance check is the important part. If item is a list, it's added unpacked to the left side of the stack. The extendleft method of deque takes iterables.

[chesschaser]

I'll try that too. Thanks for the help everyone :)

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It gave an error. :(

The class:

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class SetCategory:     def flatten(self, iterable):         stack = deque(iterable)         while stack:             item = stack.popleft()             if isinstance(item, list):                 stack.extendleft(item)             else:                 yield item       def updateNextBtn(self, evt):         if self.itemslistDuplicate.curselection() == ():             self.nextBtn.config(state = DISABLED)         else:             self.nextBtn.config(state = NORMAL)       def SET_CATEGORY(self):         global food_category_list         global confectionery_category_list         global dairy_category_list         global fruit_veg_category_list         global meat_fish_chicken_category_list         global diy_category_list         global other_category_list           category_chosen = self.categories.get()         selected = self.itemslistDuplicate.curselection()         selected_items = [[self.itemslistDuplicate.get(i) for i in self.itemslistDuplicate.curselection()]]           if category_chosen == "Food":             for i in range(0, len(str(self.flatten(selected_items)))):                 food_category_list.append(self.flatten(selected_items[i]))         elif category_chosen == "Confectionery":             for i in range(0, len(str(self.flatten(selected_items)))):                 confectionery_category_list.append(self.flatten(selected_items[i]))         elif category_chosen == "Dairy":             for i in range(0, len(str(self.flatten(selected_items)))):                 dairy_category_list.append(self.flatten(selected_items[i]))         elif category_chosen == "Fruit & Vegetables":             for i in range(0, len(str(self.flatten(selected_items)))):                 fruit_veg_category_list.append(self.flatten(selected_items[i]))         elif category_chosen == "Meat, Fish & Chicken":             for i in range(0, len(str(self.flatten(selected_items)))):                 meat_fish_chicken_category_list.append(self.flatten(selected_items[i]))         elif category_chosen == "DIY":             for i in range(0, len(str(self.flatten(selected_items)))):                 diy_category_list.append(self.flatten(selected_items[i]))         elif category_chosen == "Other":             for i in range(0, len(str(self.flatten(selected_items)))):                 other_category_list.append(self.flatten(selected_items[i]))           print(fruit_veg_category_list)                   messagebox.showinfo("Category set", "The category has been set")         self.category.destroy()       def __init__(self):         global itemslist           self.categoryItems = []           self.category = Tk()         self.category.title("OrderLog - Set item category")         self.category.attributes("-toolwindow", 1)         self.category.attributes("-topmost", 1)         self.category.geometry("300x450")           Label(self.category, text = "Set item category", font = ("Helvetica", 23)).pack(padx = 30, pady = 30)           self.categories = Combobox(self.category, state = "readonly", values = ("Food", "Confectionery", "Dairy", "Fruit & Vegetables", "Meat, Fish & Chicken", "DIY", "Other"))         self.categories.current(0)         self.categories.pack(pady = 20)           Label(self.category, text = "Select items to place in this category").pack(pady = 20)           self.itemslistDuplicate = Listbox(self.category, selectmode = "multiple")         self.itemslistDuplicate.pack(pady = 20)           for i in range(0, itemslist.size()):             self.itemslistDuplicate.insert(i, itemslist.get(i))           self.nextBtn = Button(self.category, text = "Set category", width = window.winfo_screenwidth(), state = DISABLED, command = self.SET_CATEGORY)         self.nextBtn.pack()           self.category.bind("<<ListboxSelect>>", self.updateNextBtn)

The error

Error:
Exception in Tkinter callback
Traceback (most recent call last):
  File "C:\Users\joshu\AppData\Local\Programs\Python\Python38-32\lib\tkinter\__init__.py", line 1883, in __call__
    return self.func(*args)
  File "C:/Users/joshu/Downloads/OrderLog.py", line 494, in SET_CATEGORY
    food_category_list.append(self.flatten(selected_items[i]))
IndexError: list index out of range

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And the viewing category (don't know if this shows an error or not):

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class ViewCategory:     def flatten(self, iterable):         stack = deque(iterable)         while stack:             item = stack.popleft()             if isinstance(item, list):                 stack.extendleft(item)             else:                 yield item       def viewCategoryItems(self):         global food_category_list         global confectionery_category_list         global dairy_category_list         global fruit_veg_category_list         global meat_fish_chicken_category_list         global diy_category_list         global other_category_list           self.sel_category.destroy()           self.categoryViewer = Tk()         self.categoryViewer.title("View category items")         self.categoryViewer.attributes("-toolwindow", 1)         self.categoryViewer.resizable(0, 0)           category_items = Listbox(self.categoryViewer)         category_items.pack()           flat_food_category_list = list(self.flatten(food_category_list))         flat_confectionery_category_list = list(self.flatten(confectionery_category_list))         flat_dairy_category_list = list(self.flatten(dairy_category_list))         flat_fruit_veg_category_list = list(self.flatten(fruit_veg_category_list))         flat_meat_fish_chicken_category_list = list(self.flatten(meat_fish_chicken_category_list))         flat_diy_category_list = list(self.flatten(diy_category_list))         flat_other_category_list = list(self.flatten(other_category_list))           lastItem = self.radioButtonList[-1]           if lastItem == "0":             for i in range(0, len(flat_food_category_list)):                 category_items.insert(i, str(flat_food_category_list[i]).replace("{", "").replace("}", ""))         elif lastItem == "1":             for i in range(0, len(flat_confectionery_category_list)):                 category_items.insert(i, str(flat_confectionery_category_list[i]).replace("{", "").replace("}", ""))         elif lastItem == "2":             for i in range(0, len(flat_dairy_category_list)):                 category_items.insert(i, str(flat_dairy_category_list[i]).replace("{", "").replace("}", ""))         elif lastItem == "3":             for i in range(0, len(flat_fruit_veg_category_list)):                 category_items.insert(i, str(flat_fruit_veg_category_list[i]).replace("{", "").replace("}", ""))         elif lastItem == "4":             for i in range(0, len(flat_meat_fish_chicken_category_list)):                 category_items.insert(i, str(flat_meat_fish_chicken_category_list[i]).replace("{", "").replace("}", ""))         elif lastItem == "5":             for i in range(0, len(flat_diy_category_list)):                 category_items.insert(i, str(flat_diy_category_list[i]).replace("{", "").replace("}", ""))         elif lastItem == "6":             for i in range(0, len(flat_other_category_list)):                 category_items.insert(i, str(flat_other_category_list[i]).replace("{", "").replace("}", ""))           self.radioButtonList.clear()       def foodAppend(self):         self.radioButtonList.append("0")       def confectioneryAppend(self):         self.radioButtonList.append("1")       def dairyAppend(self):         self.radioButtonList.append("2")       def fruitVegAppend(self):         self.radioButtonList.append("3")       def meatFishChickenAppend(self):         self.radioButtonList.append("4")       def diyAppend(self):         self.radioButtonList.append("5")       def otherAppend(self):         self.radioButtonList.append("6")       def __init__(self):         self.tkVariable = IntVar()         self.radioButtonList = []           self.sel_category = Tk()         self.sel_category.title("Select category to view")         self.sel_category.attributes("-toolwindow", 1)         self.sel_category.attributes("-topmost", 1)         self.sel_category.geometry("300x600")           Label(self.sel_category, text = "Select item category to view", font = ("Helvetica", 23)).pack(padx = 30, pady = 30)           self.foodOption = Radiobutton(self.sel_category, text = "Food", variable = self.tkVariable, value = 1, command = self.foodAppend)         self.foodOption.pack()           self.confectioneryOption = Radiobutton(self.sel_category, text = "Confectionery", variable = self.tkVariable, value = 2, command = self.confectioneryAppend)         self.confectioneryOption.pack()           self.dairyOption = Radiobutton(self.sel_category, text = "Dairy", variable = self.tkVariable, value = 3, command = self.dairyAppend)         self.dairyOption.pack()           self.fruitVegOption = Radiobutton(self.sel_category, text = "Fruit & Vegetables", variable = self.tkVariable, value = 4, command = self.fruitVegAppend)         self.fruitVegOption.pack()           self.meatFishChickenOption = Radiobutton(self.sel_category, text = "Meat, Fish & Chicken", variable = self.tkVariable, value = 5, command = self.meatFishChickenAppend)         self.meatFishChickenOption.pack()           self.diyOption = Radiobutton(self.sel_category, text = "DIY", variable = self.tkVariable, value = 6, command = self.diyAppend)         self.diyOption.pack()           self.otherOption = Radiobutton(self.sel_category, text = "Other", variable = self.tkVariable, value = 7, command = self.otherAppend)         self.otherOption.pack()           Label(self.sel_category).pack()           self.viewCategoryBtn = Button(self.sel_category, text = "View category items", width = 65, state = NORMAL, command = self.viewCategoryItems)         self.viewCategoryBtn.pack()

[ndc85430]

Toolz is a very useful library and its concat function may be useful.

[chesschaser]

concat? i don't want to concatenate a string.

[rielka]

1 2 3 4

import itertools origin_list = here you enter flat_list = list(itertools.chain.from_iterable(origin_list))                 print(flat_list)

[chesschaser]

Yeah. I'll try all of these if I need to

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Thanks a lot everyone! My program is fixed!