[python] Summary of how to retrieve lists and dictionary elements

Introduction

--A memorandum on how to retrieve the elements of the ``` list and dictionary --There are many other things such as adding and deleting elements, but here we will summarize only how to retrieve elements. ――What I found useful while using it is that you can combine `list` and `dictionary`. ――In particular, I personally use it most often because I can nest the `dictionary` inside the `dictionary`.

list

--A row of data of the same type --Each element is indexed in order from 0

Extract elements one by one by index

list.py

ls = ['Apple', 'Peaches', 'Cherry']
print(ls[0])
print(ls[1])
print(ls[2])

result

Apple
Peaches
Cherry

Extract elements one by one with the `` `for``` statement

list2.py

ls = ['Apple', 'Peaches', 'Cherry']
for a in ls:
    print(a)

result

Apple
Peaches
Cherry

dictionary

--A collection of data with keys and elements

Extract elements one by one by specifying a key

dic.py

dic = {'fruits':'Apple', 'Vegetables':'onion'}
print(dic['fruits'])
print(dic['Vegetables'])

result

Apple
onion

Extract the key with the `` `for``` statement

--You can get `key``` by using keys ``

dic2.py

dic = {'fruits':'Apple', 'Vegetables':'onion'}
for mykey in dic.keys():
    print(mykey)

result

fruits
Vegetables

Extract an element with a `` `for``` statement

--You can get `value``` by using values ``

dic2.py

dic = {'fruits':'Apple', 'Vegetables':'onion'}
for myval in dic.values():
    print(myval)

result

Apple
onion

Extract key and element at the same time with `` `for``` statement

--You can get both `key``` and `valueby usingitems```

dic3.py

dic = {'fruits':'Apple', 'Vegetables':'onion'}
for mykey, myval in dic.items():    
    print(mykey)
    print(myval)

result

fruits
Apple
Vegetables
onion

List in the dictionary

List value

--Elements can be retrieved with a combination of key and index

dic_list.py

dic = {'fruits':['Apple', 'Peaches'], 'Vegetables':['onion', 'carrot']}
#Extract a list of elements from a key
for mykey in dic.keys():
    for i in range(0,len(dic[mykey])):
        print(dic[mykey][i])

#Directly retrieve the list of elements
for myvalue in dic.values():
    for i in range(0,len(myvalue)):
        print(myvalue[i])

Both have the same result

result

fruits
Apple
Vegetables
onion

Dictionary in dictionary

Make `` `value``` a dictionary

--Elements can be retrieved with a combination of key and the nested dictionary `` `key```

dic_dic.py

dic = {'fruits': {'Like':'Apple', '大Like':'Peaches'}, 'Vegetables': {'Like':'Tomato', 'Hate':'green pepper'}}
print(dic['fruits']['Like'])
print(dic['Vegetables']['Hate'])

result

Apple
green pepper