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梳理总结Python开发中需要摒弃的18个坏习惯

废话不多说,我们开始学习吧!

1、拼接字符串用 + 号

坏的做法:

def manual_str_formatting(name, subscribers):
    if subscribers > 100000:
        print("Wow " + name + "! you have " + str(subscribers) + " subscribers!")
    else:
        print("Lol " + name + " that's not many subs")

好的做法是使用 f-string,而且效率会更高:

def manual_str_formatting(name, subscribers):
    # better
    if subscribers > 100000:
        print(f"Wow {name}! you have {subscribers} subscribers!")
    else:
        print(f"Lol {name} that's not many subs")

2、使用 finaly 而不是上下文管理器

坏的做法:

def finally_instead_of_context_manager(host, port):
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    try:
        s.connect((host, port))
        s.sendall(b'HelleXSXXDqo, world')
    finally:
        s.close()

好的做法是使用上下文管理器,即使发生异常,也会关闭 socket::

def finally_instead_of_context_manager(host, port):
    # close even if exception
    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
        s.connect((host, port))
        s.sendall(b'Hello, world')

3、尝试手动关闭文件

坏的做法:

def manually_calling_close_on_a_file(filename):
    f = open(filename, "w")
    f.write("hello!\n")
    f.chttp://www.cppcns.comlose()

好的做法http://www.cppcns.com是使用上下文管理器,即使发生异常,也会自动关闭文件,凡是有上下文管理器的,都应该首先采用:

def manually_calling_close_on_a_file(filename):
    with open(filename) as f:
        f.write("hello!\n")
    # close automatic, even if exception

4、except 后面什么也不写

坏的做法:

def bare_except():
    while True:
        try:
            s = input("Input a number: ")
            x = int(s)
            break
        except:  # oops! can't CTRL-C to exit
            print("Not a number, try again")

这样会捕捉所有异常,导致按下 CTRL-C 程序都不会终止,好的做法是

def bare_except():
    while True编程客栈:
        try:
            s = input("Input a number: ")
            x = int(s)
            break
        except Exception:  # 比这更好的是用 ValueError
            print("Not a number, try again")

5、函数参数使用可变对象

如果函数参数使用可变对象,那么下次调用时可能会产生非预期结果,坏的做法

def mutable_default_arguments():
    def append(n, l=[]):
        l.append(n)
        return l

    l1 = append(0)  # [0]
    l2 = append(1)  # [0, 1]

好的做法:

def mutable_default_arguments():

    def append(n, l=None):
        if l is None:
            l = []
        l.append(n)
        return l

    l1 = append(0)  # [0]
    l2 = append(1)  # [1]

6、从不用推导式

坏的做法

squares = {}
for i in range(10):
    squares[i] = i * i

好的做法

odd_squares = {i: i * i for i in range(10)}

7、推导式用的上瘾

推导式虽然好用,但是不可以牺牲可读性,坏的做法

c = [
    sum(a[n * i + k] * b[n * k + j] for k in range(n))
    for i in range(n)
    for j in range(n)
]

好的做法:

c = []
for i in range(n):
    for j in range(n):
        ij_entry = sum(a[n * i + k] * b[n * k + j] for k in range(n))
        c.append(ij_entry)

8、检查类型是否一致用 ==

坏的做法

def checking_type_equality():
    Point = namedtuple('Point', ['x', 'y'])
    p = Point(1, 2)

    if type(p) == tuple:
        print("it's a tuple")
    else:
        print("it's not a tuple")

好的做法

def checkhttp://www.cppcns.coming_type_equality():
    Point = namedtuple('Point', ['x', 'y'])
    p = Point(1, 2)

    # probably meant to check if is instance of tuple
    if isinstance(p, tuple):
        print("it's a tuple")
    else:
        print("it's not a tuple")

9、用 == 判断是否单例

坏的做法

def equality_for_singletons(x):
    if x == None:
        pass

    if x == True:
        pass

    if x == False:
        pass

好的做法

def equality_for_singletons(x):
    # better
    if x is None:
        pass

    if x is True:
        pass

    if x is False:
        pass

10、判断一个变量用 bool(x)

坏的做法

def checking_bool_or_len(x):
    if bool(x):
        pass

    if len(x) != 0:
        pass

好的做法

def checking_bool_or_len(x):
    # usually equivalent to
    if x:
        pass

11、使用类 C 风格的 for 循环

坏的做法

def range_len_pattern():
    a = [1, 2, 3]
    for i in range(len(a)):
        v = a[i]
        ...
    b = [4, 5, 6]
    for i in range(len(b)):
        av = a[i]
        bv = b[i]
        ...

好的做法

def range_len_pattern():
    a = [1, 2, 3]
    # instead
    for v in a:
        ...

    # or if you wanted the index
    for i, v in enumerate(a):
        ...

    # instead use zip
    for av, bv in zip(a, b):
        ...

12、不实用 dict.items

坏的做法

def not_using_dict_items():
    d = {"a": 1, "b": 2, "c": 3}
    for key in d:
        val = d[key]
        ...

好的做法

def not_using_dict_items():
    d = {"a": 1, "b": 2, "c": 3}
    for key, val in d.items():
        ...

13、解包元组使用索引

坏的做法

mytuple = 1, 2
x = mytuple[0]
y = mytuple[1]

好的做法

mytuple = 1, 2
x, y = mytuple

14、使用 time.time() 统计耗时

坏的做法

def timing_with_time():
    start = time.time()
    time.sleep(1)
    end = time.time()
    print(end - start)

好的做法是使用 time.perf_counter(),更精确:

def timing_with_time():
   # more accurate
    start = time.perf_counter()
    time.sleep(1)
    end = time.perf_counter()
    print(end - start)

15、记录日志使用 print 而不是 logging

坏的做法

def print_vs_logging():
    print("debug info")
    print("just some info")
    print("bad error")

好的做法

def print_vs_logging():
    # versus
    # in main
    level = logging.DEBUG
    fmt = '[%(levelname)s] %(asctime)s - %(message)s'
    logging.basicConfig(level=level, format=fmt)

    # wherever
    logging.debug("debug info")
    logging.info("just some info")
    logging.error("uh oh :(")

16、调用外部命令时使用 shell=True

坏的做法

subprocess.run(["ls -l"], capture_output=True, shell=True)

如果 shell=True,则将 ls -l 传递给/bin/sh(shell) 而不是 Unix 上的 ls 程序,会导致 subprocess 产生一个中间 shell 进程, 换句话说,使用中间 shell 意味着在命令运行之前,命令字符串中的变量、glob 模式和其他特殊的 shell 功能都会被预处理。比如,$HOME 会在在执行 echo 命令之前被处理处理。

好的做法是拒绝从 shell 执行:

subprocess.run(["ls", "-l"], capture_output=True)

17、从不尝试使用 numpy

坏的做法

def not_using_numpy_pandas():
    x = list(range(100))
    y = list(range(100))
    s = [a + b for a, b in zip(x, y)]

好的做法:

import numpy as np
def not_using_numpy_pandas():
    # 性能更快
    x = np.arange(100)
    y = np.arange(100)
    s = x + y

18、喜欢 import *

坏的做法

from itertools import *

count()

这样的话,没有人直到这个脚本到底有多数变量, 好的做法:

from mypackage.nearby_module import awesome_function

def main():
    awesome_function()

if __name__ == '__main__':
    main()

到此这篇关于梳理总结python开发中需要摒弃的18个坏习惯的文章就介绍到这了,更多相关Python 坏习惯内容请搜索我们以前的文章或继续浏览下面的相关文章希望大家以后多多支持我们!

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