Hallo Habr! Ich präsentiere Ihnen die Übersetzung des Artikels "Lesezeichen setzen, wenn Sie neu in Python sind (insbesondere wenn Sie Python selbst lernen)" in zwei Teilen ( 1 , 2 ) mit einfachen, aber nützlichen Tipps und Tricks in 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
>>> 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
>>> 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
True
>>> a>=b
False
>>> a.union(b)
{1, 2, 3, 4, 5}
>>> a.intersection(b)
{1, 2, 3}
>>> a.difference(b)
set()
>>> 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}
Zusätzliche Informationen: Sammlungen
Fazit
Obwohl diese Tricks recht einfach sind, können sie Zeit sparen und Ihren Code vereinfachen. Ich hoffe, dieser Artikel hat Ihnen geholfen, herauszufinden, wie Sie die einfachen Funktionen von Python verwenden können. Gutes Training und Code. Bis zum nächsten Mal.