from IPython.core.interactiveshell import InteractiveShell
InteractiveShell.ast_node_interactivity = "all"
x = [0, 1, [2]]
x[2][0] = 3
print(x)
x[2].append(4)
print(x)
x[2] = 2
print(x)[0, 1, [3]] [0, 1, [3, 4]] [0, 1, 2]
sum([1, 2, 3])6
# list cheatsheet
# How to create an empty array?
l = [] #square brackets
l = list()
l[]
# How to create a literal array
l = [1,2,3]n = [int(num) for num in l]
n[1, 2, 3]
# how to find the number of elements in an array
len(l)3
# how to access elements in an array
l[0]1
# how to slice an array
l[0:2] #last index always excluded[1, 2]
#how to update the value at a given position
l[1] = 5
l[1, 5, 3]
#how to read and update the value at a given position
l[1] = l[1] + 2
l[1] += 2
l[1, 9, 3]
#How to list all the methods of an array
dir(l) #list of all methods, but the function with this '__' is only intern usage['add',
'class',
'contains',
..
'append',
'clear',
..
'reverse', 'sort']
#How to the documentation of a method
help(l.remove)Help on built-in function remove:
remove(value, /) method of builtins.list instance Remove first occurrence of value.
Raises ValueError if the value is not present.
#how to add new values at hen end of the array
l.append(5)#how to insert new values at a given index
l.insert(3,7)
l[1, 9, 3, 7, 5]
#How to remove the value at the end
l.pop()
l5
[1, 9, 3, 7]
# how to remove the value at a given index
l.remove(3)
l[1, 9, 7]
l.pop(2)7
l.append(22)
del l[1]1
[1, 22]
#How to remove all the elements in an array
l.clear()
del l[:]# how to find an element in an array
l = ["a","b","c","d"]
"c" in l #exists?True
l.index("c")2
l.reverse()
l['d', 'c', 'b', 'a']
l[::-1]
l['a', 'b', 'c', 'd']
['d', 'c', 'b', 'a']
l.sort()sorted(l)['a', 'b', 'c', 'd']
l1 = ["a","b","c"]
l2 = ["d","e","f"]
l3 = l1 + l2
l3['a', 'b', 'c', 'd', 'e', 'f']
l3.extend(l2) #Modifies the original array
l=l1 + l2 #Returns a new list# How to copy an array
l4 = l1 #ERROR!!! NO COPY!!! It's a pointer
l4
l1.append('z')
l4['a', 'b', 'c']
['a', 'b', 'c', 'z']
#copy
l4 = l1.copy() #Shallow copy only objects without nested lists, nested lists point to original object
l1.append('w')
l1['a', 'b', 'c', 'z', 'w']
l4 #its object different['a', 'b', 'c', 'z']
import copy
l4=copy.deepcopy(l1) #Deep copy it's the best option.x1 = [{'a':1},{'b':2}]
x2 = x1.copy()
x2[0]["a"] = 3 #modificas también el x1
x1[{'a': 3}, {'b': 2}]
x1 = [{'a':1},{'b':2}]
import copy
x2 = copy.deepcopy(x1)
x2[0]["a"] = 3 #no lo modificas
x1[{'a': 1}, {'b': 2}]
#How to delete a slice
del l4[0:2]#How to delete an array
del l4# How to create an empty dict
dictionary = {}# How to create a populated literal dict
dictionary = {"name":"Miquel","surname":"Bardaji","age":30}# How to create a dict form a list of tuples
my_list = [('a', 1), ('b', 2)]
dict(my_list){'a': 1, 'b': 2}
# How to create a dict form two lists
keys_list = ["a","b","c"]
values_list = [1,2,3]
tuple_list=list(zip(keys_list, values_list))
d = dict(zip(keys_list,values_list))
print("tuple_list:", tuple_list)
d= dict(tuple_list)tuple_list: [('a', 1), ('b', 2), ('c', 3)]
# How to find the number of items in a dict
len(d)3
# How to list all the methods in a dict
dir(d)['class',
'contains',
'delattr',
'delitem',
..
'clear',
'copy',
..
'update',
'values']
# How to list items
list(d.items())[('a', 1), ('b', 2), ('c', 3)]
# How to list keys
list(d.keys())['a', 'b', 'c']
# How to list values
list(d.values())[1, 2, 3]
# How to access an element in an dict
d["a"]
d.get("z","No encontrado")1
'No encontrado'
# How to add a new element to a dict
d["d"] = 0# How to update a value in a dict
d["d"] = 10
d{'a': 1, 'b': 2, 'c': 3, 'd': 10}
# How to read and update a value in a dict
d["d"] = d["d"]+3
d{'a': 1, 'b': 2, 'c': 3, 'd': 13}
# How to add all items from one dict to another dict
d2 = {"d":4,"c":3,"f":5}
d.update(d2)
d{'a': 1, 'b': 2, 'c': 3, 'd': 4, 'f': 5}
# How to remove a specific item and retrieve the value
"f" in d #Test if it existTrue
d.pop("f")5
# How to sort a dict
d = {"c":3,"b":2,"d":4,"a":1}
sorted_keys = sorted(d.keys())
sorted_values = [d[k] for k in sorted_keys]
sorted_dict = dict(zip(sorted_keys,sorted_values))
print("sorted:", sorted_keys)
print("sorted_values",sorted_values)
print("sorted_dict",sorted_dict)sorted: ['a', 'b', 'c', 'd']
sorted_values [1, 2, 3, 4]
sorted_dict {'a': 1, 'b': 2, 'c': 3, 'd': 4}
# How to delete one item in a dict
d["w"] = 4
d{'c': 3, 'b': 2, 'd': 4, 'a': 1, 'w': 4}
del d["w"]
d{'c': 3, 'b': 2, 'd': 4, 'a': 1}
# How to copy a dict
import copy
d4 = copy.deepcopy(d)
d4{'c': 3, 'b': 2, 'd': 4, 'a': 1}
# How to delete a dict
del d4# How to delete a list of keys
keys_delete = ["b","d"]
for k in keys_delete:
d.pop(k)
d2
4
{'c': 3, 'a': 1}