Python标准库中的9个高效编程技巧：从字符串处理到资源限制

user_input = "This 
string has some whitespaces... 
" 
character_map = { 
  ord(  
 ) :  , 
  ord(   ) :  , 
  ord(  
 ) : None 
} 
user_input.translate(character_map) # This string has some whitespaces... 

import itertools 
s = itertools.islice(range(50), 10, 20) # <itertools.islice object at 0x7f70fab88138> 
for val in s: 
  ... 

string_from_file = """ 
// Author: ... 
// License: ... 
// 
// Date: ... 
Actual content... 
 """ 
import itertools 
for line in itertools.dropwhile(lambda line: line.startswith("//"), string_from_file.split(" 
")): 
  print(line) 

def test(*, a, b): 
  pass 
test("value for a", "value for b") # TypeError: test() takes 0 positional arguments... 
test(a="value", b="value 2") # Works... 

class Connection: 
  def __init__(self): 
    ... 
  def __enter__(self): 
    # Initialize connection... 
  def __exit__(self, type, value, traceback): 
    # Close connection... 
with Connection() as c: 
  # __enter__() executes 
  ... 
  # conn.__exit__() executes 

from contextlib import contextmanager 
@contextmanager 
def tag(name): 
  print(f"<{name}>") 
  yield 
  print(f"</{name}>") 
with tag("h1"): 
  print("This is Title.") 

class Person: 
  __slots__ = ["first_name", "last_name", "phone"] 
  def __init__(self, first_name, last_name, phone): 
    self.first_name = first_name 
    self.last_name = last_name 
    self.phone = phone 

import signal 
import resource 
import os 
# To Limit CPU time 
def time_exceeded(signo, frame): 
  print("CPU exceeded...") 
  raise SystemExit(1) 
def set_max_runtime(seconds): 
  # Install the signal handler and set a resource limit 
  soft, hard = resource.getrlimit(resource.RLIMIT_CPU) 
  resource.setrlimit(resource.RLIMIT_CPU, (seconds, hard)) 
  signal.signal(signal.SIGXCPU, time_exceeded) 
# To limit memory usage 
def set_max_memory(size): 
  soft, hard = resource.getrlimit(resource.RLIMIT_AS) 
  resource.setrlimit(resource.RLIMIT_AS, (size, hard)) 

def foo(): 
  pass 
def bar(): 
  pass 
__all__ = ["bar"] 

from functools import total_ordering 
@total_ordering 
class Number: 
  def __init__(self, value): 
    self.value = value 
  def __lt__(self, other): 
    return self.value < other.value 
  def __eq__(self, other): 
    return self.value == other.value 
print(Number(20) > Number(3)) 
print(Number(1) < Number(5)) 
print(Number(15) >= Number(15)) 
print(Number(10) <= Number(2))