Python Built-in Functions

print

for i in range(4):
    print("?", end="")
print()

Default end is new line. Specify end to avoid \n

chr ord

x = ord('A') 
print(x)
y = chr(65) 
print(y)
output:
65
A
 
print(chr(ord('ć'))) 
print(ord(chr(65)))
 
output:
ć 
65

sort() sorted()

sorted() can sort everything, return a list, won’t change anything
sort() sort immediately

Key can be the length, or the return value of a function, to be called on each list element prior to making comparisons. And Lambda and Anonymous Function
here’s a case-insensitive string comparison:
sorted("This is a test string from Andrew".split(), key=str.lower)
A common pattern is to sort complex objects using some of the object’s indices as keys. For example:

>>> student_tuples = [
...     ('john', 'A', 15),
...     ('jane', 'B', 12),
...     ('dave', 'B', 10),
... ]
>>> sorted(student_tuples, key=lambda student: student[2])   # sort by age
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]

map

map() 是 Python 内置的高阶函数，它接收一个函数 f 和一个 list，并通过把函数 f 依次作用在 list 的每个元素上，得到一个新的 list 并返回。

def addition(n):
    return n + n
  
# We double all numbers using map()
numbers = (1, 2, 3, 4)
result = map(addition, numbers)
print(list(result))
[2, 4, 6, 8]
 
numbers = (1, 2, 3, 4)
result = map(lambda x: x + x, numbers)
print(list(result))
[2, 4, 6, 8]
 
l = ['sat', 'bat', 'cat', 'mat']
  
# map() can listify the list of strings individually
test = list(map(list, l))
print(test)

zip

The zip() function takes iterables (can be zero or more), aggregates them in a tuple, and returns it.

languages = ['Java', 'Python', 'JavaScript']
versions = [14, 3, 6]
 
result = zip(languages, versions)
print(list(result))
 
# Output: [('Java', 14), ('Python', 3), ('JavaScript', 6)]

enumerate

index + content
Python Docs

>>> for i, v in enumerate(['tic', 'tac', 'toe']):
...     print(i, v)
...
0 tic
1 tac
2 toe

reversed() and sorted()

>>> for i in reversed(range(1, 10, 2)):
...     print(i)
...
9
7
5
3
1
 
>>> basket = ['apple', 'orange', 'apple', 'pear', 'orange', 'banana']
>>> for i in sorted(basket):
...     print(i)
...
apple
apple
banana
orange
orange
pear

reduce

from functools import reduce
print(functools.reduce(lambda a, b: a+b, lis))

remove

remove via index
已知 x = [1, 2, 3, 2, 3],执行语句 x.remove(2) 之后,x = [1, 3, 2, 3]

Fish Touching🐟🎣

Explorer