Cheatography

# Python_Chap_4 Cheat Sheet by Theo666

lists : a collection of items that are ordered and mutable

### Lists

A list is a data structure that contains a series of values. Python allows the constr­uction of a list containing values of different types. It's iterable, indexable, ordered, mutable and not hashable.

### combin­ation of lists and dictio­naries

 [[...], [...], [...], ...] list of list list_o­f_l­ist­[...][...] index elements in a list of list dict{key : [..., ...]} values of a dictionary can be a list [dict1, dict2] list of dictionary
But the keys of dictionary are hasables, not ordered and not duplic­ated.
list[:] is a new list duplic­ating the original, so list[:] will return the first element of the list

### Operation in the lists

 list + list add lists list * int multiply the list
- We cannont substract directly a list from another by using ' - ' . [ i for i in list1 if i not in list2]; set(list1) - set(list2)
- To repeat each element of lists, [i for i in list for _ in range(­int)]
- list_1 += list_2 equal to list_1 = list_1 + list_2

### Common Functions

 ``list[s­tar­t:s­top­:step]`` list sciling (tranche) ``enumer­ate­(list)`` return positions and items ``list.i­nde­x(item)`` return the position of the item ``list.c­oun­t(item)`` returns the number of times that element appears in the list ``list(s­tring)`` convert a string to a list one by one charcter ``string.sp­lit­(sep)`` convert a string to a list with a separator ``'sep'.j­oi­n(list)`` convert a list to a string ``len(list)`` length of lists ``max(list)`` find the maximun ``min(list)`` find the minimun ``sum(list)`` calculate the sum ``list.s­ort­(re­verse=)`` sort the elements of a list in-place. reverse False from smallest to largest values; alphabetic order possible ``sorted­(list, reverse=)`` create a new sorted list without modifying the original list; alphabetic order possible ``list.r­eve­rse()`` reverse the elements of a list in-place ``revers­ed(­list)`` create a new reversed list without modifying the original list ``list.a­ppe­nd(­item)`` add an element to the end of lists ``list.i­nse­rt(­item, pos)`` insert an element at a position of lists ``list.r­emo­ve(­item)`` remove an item from lists; remove only one first element. ``list.pop()`` remove and return the last element ``del list[pos]`` remove the item by its position idenx ``range(­sta­rt,­sto­p,step)`` similar to lists, but immutable. stop at n-1 ``set(list)`` remove the duplicated elements
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``list[s­tar­t:s­top­:step]``
step 1 by default; stop at n-1 even if negative index
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``list[:]``
create a new list. lst2 = lst1 creates a reference to the original list with the same ID
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``'sep'.j­oi­n(list)``
cannot combine a list containing only number (int & float). [str(i) for i in list]
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``list.r­emo­ve(­item)``
If there're duplicated elements, it remove only the first element
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``range(­sta­rt,­sto­p,step)``