Olá Habr! Apresento a você a tradução do artigo "Marque isto se você é novo no Python (especialmente se você aprender a aprender Python)" em duas partes ( 1 , 2 ) com dicas e truques simples, mas úteis, em Python.

- Python, . . , Python, , .. , Python . , Python , , .

: Python 3.8. - , , , Python.

>>> a = 1
>>> b = 3
>>> a == 1
True
>>> a == 2
False
>>> a == b
False
>>> a > b
False
>>> a <= b
True
>>> if a <= b :
...     print('a is less than or equal to b')
...
a is less than or equal to b

. True False. if-else.

>>> def compare(a,b):
...     if a> b:
...             return a
...     else:
...             return b
...

return.

>>> def compare(a, b):
...     return a if a > b else b
...

/

>>> arr_list = [1,4,7]
>>> a = arr_list[0]
>>> b = arr_list[1]
>>> c = arr_list[2]

, :

>>> a, b, c = arr_list
>>> a
1
>>> b
4
>>> c
7

>>> arr_list = [1,4,7]
>>> result = []
>>> for i in arr_list:
...     result.append(i*2)
...
>>> result
[2, 8, 14]

>>> result = [x*2 for x in arr_list]
>>> result
[2, 8, 14]

zip

>>> a = [1,5,8]
>>> b = [3,4,7]
>>> result = []
>>> for i in range(len(a)):
...     result.append(a[i] if a[i] < b[i] else b[i])
...
>>> result
[1, 4, 7]

>>> result = [min(i) for i in zip(a,b)]
>>> result
[1, 4, 7]

lambda

>>> arr_list= [[1,4], [3,3], [5,7]]
>>> arr_list.sort(key=lambda x: x[1])
>>> arr_list
[[3, 3], [1, 4], [5, 7]]

filter, map

>>> arr_list = [-1, 1, 3, 5]
>>> result = []
>>> for i in arr_list:
...     if i > 0:
...             result.append(i**2)
...
>>> result
[1, 9, 25]

>>> result = list(map(lambda x: x**2, filter(lambda x: x > 0, arr_list)))
>>> result
[1, 9, 25]

: -, :)

Oleg Kapustin Kuldeep Pal.

>>> result = [i**2 for i in arr_list if i > 0]
>>> result
[1, 9, 25]

,

set , , .

>>> arr_list = [1,4,4,6,9]
>>> len(arr_list) == len(set(arr_list))
False

>>> pi = 3.14159
#  Python3.6
>>> print('The value of pi is {:.2f}'.format(pi))
The value of pi is 3.14

>>> a, b, c = 1,5,9
>>> print('a is {}; b is {}; c is {}'.format(a,b,c))
a is 1; b is 5; c is 9

#  Python3.6+
>>> print(f'The value of pi is {pi:.2f}')
The value of pi is 3.14
>>> pi
3.14159

>>> print(f'a is {a}; b is {b}; c is {c}')
a is 1; b is 5; c is 9

: PyFormat

enumerate

>>> arr_list = [1, 5, 9]
>>> for i in range(len(arr_list)):
...     print(f'Index: {i}; Value: {arr_list[i]}')
...
Index: 0; Value: 1
Index: 1; Value: 5
Index: 2; Value: 9

>>> for i, j in enumerate(arr_list):
...     print(f'Index: {i}; Value: {j}')
...
Index: 0; Value: 1
Index: 1; Value: 5
Index: 2; Value: 9

>>> arr_list = [1,4,6,8,10,11]
>>> a, *b, c = arr_list
>>> a
1
>>> b
[4, 6, 8, 10]
>>> c
11

itertools

>>> str_list = ['A', 'C', 'F']
>>> list(itertools.combinations(str_list,2))
[('A', 'C'), ('A', 'F'), ('C', 'F')]
>>> list(itertools.permutations(str_list,2))
[('A', 'C'), ('A', 'F'), ('C', 'A'), ('C', 'F'), ('F', 'A'), ('F', 'C')]

>>> a = 5
>>> b = 8
>>> temp = a
>>> a = b
>>> b = temp + a
>>> a
8
>>> b
13

. .

>>> a = 5
>>> b = 8
>>> a,b = b, a+b
>>> a
8
>>> b
13

(PS: ? !)

: Evaluation order

>>> str_list = ['This', 'is', 'WYFok']
>>> ' '.join(str_list)
'This is WYFok'

, , join. .

>>> ans_list = [3,6,9]
>>> 'The answer is '+','.join(map(str,ans_list))
'The answer is 3,6,9'

map , join .

: str.join, map

Underscore ()

, , for, :

>>> for i in range(3):
...     print('Hello')
...
Hello
Hello
Hello

, i for. i _ (). ( _ – , Python . , .)

>>> for _ in range(3):
...     print('Hello')
...
Hello
Hello
Hello

Dict.keys, Dict.values, Dict.items

>>> teacher_subject = {'Ben':'English','Maria':'Math','Steve':'Science'}
>>> teacher_subject.keys()
dict_keys(['Ben', 'Maria', 'Steve'])
>>> teacher_subject.values()
dict_values(['English', 'Math', 'Science'])
>>> teacher_subject.items()
dict_items([('Ben', 'English'), ('Maria', 'Math'), ('Steve', 'Science')])

keys values . items , . , .

>>> subject_teacher = {y:x for x,y in teacher_subject.items()}
>>> subject_teacher
{'English': 'Ben', 'Math': 'Maria', 'Science': 'Steve'}

: , .

(: zip )

>>> subject = ['English','Math','Scienc']
>>> teacher = ['Ben','Maria','Steve']
>>> subject_teacher = {f:v for f,v in zip(subject,teacher)}
>>> subject_teacher
{'English': 'Ben', 'Math': 'Maria', 'Scienc': 'Steve'}

: Mapping Types — dict

>>> a = {1,2,3}
>>> b = {1,2,3,4,5}
# a  b?
>>> a<=b
True
# b  a?
>>> a>=b
False
#  a  b 
>>> a.union(b)
{1, 2, 3, 4, 5}
#  a  b 
>>> a.intersection(b)
{1, 2, 3}
#  
#    a,    b 
>>> a.difference(b)
set()
#    b,    a
>>> b.difference(a)
{4, 5}

: Set

collections.Counter

, . Counter, .

>>> import collections
>>> arr_list = [1,1,1,1,2,2,2,3,3,5,5,5,7]
>>> c = collections.Counter(arr_list)
>>> c
Counter({1: 4, 2: 3, 5: 3, 3: 2, 7: 1})
>>> type(c)
<class 'collections.Counter'>
>>> c[1]
4
>>> c[6]
0
#    
>>> dict(c)
{1: 4, 2: 3, 3: 2, 5: 3, 7: 1}

Informações adicionais: collections.Counter

Conclusão

Embora esses truques sejam bastante simples, eles podem ajudar a economizar tempo e simplificar seu código. Espero que este artigo tenha ajudado você a descobrir como usar os recursos simples do Python. Bom treinamento e código. Vejo você na próxima vez.

Marque este artigo como favorito se você é novo no Python (especialmente se você mesmo estiver aprendendo Python)

/

zip