Python程序最佳风格：你有什么建议？
我有个朋友想学编程，于是他把他之前上课写的所有程序都给了我。最后一个他写的程序是一个加密程序，我把他所有的程序都用Python重写了一遍，这就是我在加密程序中加入自己要求后得到的结果。
#! /usr/bin/env python
################################################################################
"""\
CLASS INFORMATION
-----------------
Program Name: Program 11
Programmer: Stephen Chappell
Instructor: Stephen Chappell for CS 999-0, Python
Due Date: 17 May 2010
DOCUMENTATION
-------------
This is a simple encryption program that can encode and decode messages."""
################################################################################
import sys
KEY_FILE = 'Key.txt'
BACKUP = '''\
!"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNO\
PQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~
_@/6-UC'GzaV0%5Mo9g+yNh8b">Bi=<Lx [sQn#^R.D2Xc(\
Jm!4e${lAEWud&t7]H\`}pvPw)FY,Z~?qK|3SOfk*:1;jTrI''' #`
################################################################################
def main():
"Run the program: loads key, runs processing loop, and saves key."
encode_map, decode_map = load_key(KEY_FILE)
try:
run_interface_loop(encode_map, decode_map)
except SystemExit:
pass
save_key(KEY_FILE, encode_map)
def run_interface_loop(encode_map, decode_map):
"Shows the menu and runs the appropriate command."
print('This program handles encryption via a customizable key.')
while True:
print('''\
MENU
====
(1) Encode
(2) Decode
(3) Custom
(4) Finish''')
switch = get_character('Select: ', tuple('1234'))
FUNC[switch](encode_map, decode_map)
def get_character(prompt, choices):
"Gets a valid menu option and returns it."
while True:
sys.stdout.write(prompt)
sys.stdout.flush()
line = sys.stdin.readline()[:-1]
if not line:
sys.exit()
if line in choices:
return line
print(repr(line), 'is not a valid choice.')
################################################################################
def load_key(filename):
"Gets the key file data and returns encoding/decoding dictionaries."
plain, cypher = open_file(filename)
return dict(zip(plain, cypher)), dict(zip(cypher, plain))
def open_file(filename):
"Load the keys and tries to create it when not available."
while True:
try:
with open(filename) as file:
plain, cypher = file.read().split('\n')
return plain, cypher
except:
with open(filename, 'w') as file:
file.write(BACKUP)
def save_key(filename, encode_map):
"Dumps the map into two buffers and saves them to the key file."
plain = cypher = str()
for p, c in encode_map.items():
plain += p
cypher += c
with open(filename, 'w') as file:
file.write(plain + '\n' + cypher)
################################################################################
def encode(encode_map, decode_map):
"Encodes message for the user."
print('Enter your message to encode (EOF when finished).')
message = get_message()
for char in message:
sys.stdout.write(encode_map[char] if char in encode_map else char)
def decode(encode_map, decode_map):
"Decodes message for the user."
print('Enter your message to decode (EOF when finished).')
message = get_message()
for char in message:
sys.stdout.write(decode_map[char] if char in decode_map else char)
def custom(encode_map, decode_map):
"Allows user to edit the encoding/decoding dictionaries."
plain, cypher = get_new_mapping()
for p, c in zip(plain, cypher):
encode_map[p] = c
decode_map[c] = p
################################################################################
def get_message():
"Gets and returns text entered by the user (until EOF)."
buffer = []
while True:
line = sys.stdin.readline()
if line:
buffer.append(line)
else:
return ''.join(buffer)
def get_new_mapping():
"Prompts for strings to edit encoding/decoding maps."
while True:
plain = get_unique_chars('What do you want to encode from?')
cypher = get_unique_chars('What do you want to encode to?')
if len(plain) == len(cypher):
return plain, cypher
print('Both lines should have the same length.')
def get_unique_chars(prompt):
"Gets strings that only contain unique characters."
print(prompt)
while True:
line = input()
if len(line) == len(set(line)):
return line
print('There were duplicate characters: please try again.')
################################################################################
# This map is used for dispatching commands in the interface loop.
FUNC = {'1': encode, '2': decode, '3': custom, '4': lambda a, b: sys.exit()}
################################################################################
if __name__ == '__main__':
main()
对于所有的Python程序员们，我需要你们的帮助。关于格式方面（不一定是代码本身），应该怎么调整才能符合Python的风格指南呢？我朋友不需要学到不正确的东西。如果你们对代码有建议，也欢迎把它们发到这个wiki上。
编辑：对那些感兴趣的人，这里是我朋友给我的原始C语言代码，供翻译用。
/******************************************************************************
CLASS INFORMATION
-----------------
Program Name: Program 11 - Encodes/Decodes
Programmer: Evgnto nAl.Wi a
Instructor: fsSP21 .C emgr2rCHoMal4 gyia ro-rm n ,
Date Due: MAY 4, 2010
PLEDGE STATEMENT
----------------
I pledge that all of the code in this program is my own _original_ work for
the spring 2010 semester. None of the code in this program has been copied
from anyone or anyplace unless I was specifically authorized to do so by my
CS 214 instructor. This program has been created using properly licensed
software.
Signed: ________________________________
DOCUMENTATION
-------------
This program Encodes and decodes a program. It also gives you the option of
making your own code.
******************************************************************************/
#include <stdio.h>
#define ENCODE 1
#define DECODE 2
#define OWNCODE 3
#define QUIT 4
void printPurpose();
void encode(char input[], char code1[]);
void decode(char input[], char code1[]);
void ownCode();
int main()
{
char charIn;
char code1[100] = "";
char input[100] = "";
int a;
int b;
int closeStatus;
int number;
a = 0;
b = 0;
FILE *code;
printPurpose();
if (!(code = fopen("code.txt", "r")))
{
printf("Error opening code.txt for reading");
return 100;
}
while ((charIn = fgetc(code)) != '\n')
{
input[a] = charIn;
a++;
}
while ((charIn = fgetc(code)) != EOF)
{
code1[b] = charIn;
b++;
}
scanf("%d", &number);
while (number != QUIT)
{
if (number == ENCODE)
encode(input, code1);
else if (number == DECODE)
decode(input, code1);
else if (number == OWNCODE)
ownCode();
printf("\n\n");
printPurpose();
scanf("%d", &number);
}
printf("Thank you for using my program Mr. Halsey!!!!!!!!\n");
closeStatus = fclose(code);
if (closeStatus == EOF)
{
printf("File close error.\n");
return 201;
}
else
printf("Exit successfully.\n");
return 0;
}
/******************************************************************************
Prints the purpose of the program
******************************************************************************/
void printPurpose()
{
printf("This program Encodes, Decodes, and allows you to make your own");
printf("code.\n");
printf("Enter a 1 to Encode\n");
printf("Enter a 2 to Decode\n");
printf("Enter a 3 to make your own code\n");
printf("Enter a 4 to Quit\n");
}
/******************************************************************************
Encodes the sentence entered
******************************************************************************/
void encode(char input[], char code1[])
{
char sentence[100] = "";
char x;
char y;
int index;
int index2;
index = 0;
printf("Enter your sentence\n");
gets(sentence);
gets(sentence);
printf("Your encoded message is >");
for (index2 = 0; (y = sentence[index2]) != '\0'; index2++)
{
while ((x = input[index]) != y)
index++;
if (x == y)
printf("%c", code1[index]);
else
printf("error");
index = 0;
}
return;
}
/******************************************************************************
Decodes the sentence entered
******************************************************************************/
void decode(char input[], char code1[])
{
char encodedMessage[100] = "";
char x;
char y;
int index1;
int index2;
index2 = 0;
printf("Enter encoded message\n");
gets(encodedMessage);
gets(encodedMessage);
printf("Your decoded message is >");
for (index1 = 0; (y = encodedMessage[index1]) != '\0'; index1++)
{
while (( x = code1[index2]) != y)
index2++;
if (x == y)
printf("%c", input[index2]);
else
printf("error");
index2 = 0;
}
return;
}
/******************************************************************************
Reads in your code and encodes / decodes
******************************************************************************/
void ownCode()
{
char charactersUsed[50] = "";
char codeUsed[50] = "";
char sentence[50] = "";
int index1;
int index2;
int number;
int x;
int y;
index2 = 0;
y = 0;
printf("Enter the characters you want to use.\n");
printf("Use less than 50 characters and DO NOT REPEAT the characters.\n");
gets(charactersUsed);
gets(charactersUsed);
printf("Enter the code for the characters.\n");
gets(codeUsed);
printf("\nEnter 1 to encode and 2 to decode or 3 to return to main menu.\n");
scanf("%d", &number);
while (number != OWNCODE)
{
if (number == ENCODE)
{
printf("Enter your sentence.\n");
gets(sentence);
gets(sentence);
printf("Your encoded message is > ");
for (index1 = 0; (y = sentence[index1]) != '\0'; index1++)
{
while (( x = charactersUsed[index2]) != y)
index2++;
if (x == y)
printf("%c", codeUsed[index2]);
else
printf("error");
index2 = 0;
}
}
else if (number == DECODE)
{
printf("Enter your encoded sentence.\n");
gets(sentence);
gets(sentence);
printf("Your decoded message is > ");
for (index1 = 0; (y = sentence[index1]) != '\0'; index1++)
{
while (( x = codeUsed[index2]) != y)
index2++;
if (x == y)
printf("%c", charactersUsed[index2]);
else
printf("error");
index2 = 0;
}
}
printf("\nEnter 1 to encode and 2 to decode or 3 to return to main menu.\n");
scanf("%d", &number);
}
return;
}
5 个回答
3
在我看来，这个程序整体上有点问题。把功能分成不同的函数的方式有点傻，而且文档写得像是一个班级项目，而不是一个真正的系统。文档有点遮掩了整体上平庸的组织结构。整个程序更倾向于冗长而不是清晰。
你会经常看到这个构造 '''\。三重引号的作用是可以很方便地使用换行符和回车符，不需要用 \ 来转义换行。
我会挑一些我看到具体问题的函数来举例：
关于 get_message 是否应该以那种形式存在是有争议的。整个函数其实可以用一行代码替代。
def get_message():
"Gets and returns text entered by the user (until EOF)."
return sys.stdin.read()
函数 main、run_interface_loop、get_character 和 FUNC 之间的互动让人困惑，这并不是处理问题的最佳方式。特别是，捕获 SystemExit 在这种情况下并不是一个很好的结束程序的信号。
def main():
encode_map, decode_map = load_key(KEY_FILE)
run_interface_loop(encode_map, decode_map)
save_key(KEY_FILE, encode_map)
def run_interface_loop():
exit_picked = False
while not exit_picked:
print '''
MENU
====
(1) Encode
(2) Decode
(3) Custom
(4) Finish'''
choice = sys.stdin.readline()
if choice == '':
break # EOF was reached, no more asking the user for stuff
choice = choice.strip()
if choice == '1':
encode(encode_map, decode_map) # This reads until EOF
exit_picked = True # and so we might as well exit
elif choice == '2':
decode(encode_map, decode_map)
exit_picked = True # Same here
elif choice == '3':
encode_map, decode_map = custom()
elif choice == '4':
exit_picked = True
else:
print "%s isn't a valid choice, try again." % (choice,)
6
不要使用裸的异常捕获;
try:
with open(filename) as file:
plain, cypher = file.read().split('\n')
return plain, cypher
**except:**
with open(filename, 'w') as file:
file.write(BACKUP)
几乎总是错误地使用裸的异常捕获，在这种情况下也是错的。你应该只捕获你想要处理的异常，这里最可能的是IOException（输入输出异常），还有如果文件里没有'\n'导致你的元组解包失败时可能出现的错误（提示：把它们放在不同的异常捕获块中）。另外，你可能还想检查一下，如果用户没有对文件名的写权限，会发生什么。
你为什么不在这里使用print和raw_input()呢？
def get_character(prompt, choices):
"Gets a valid menu option and returns it."
while True:
sys.stdout.write(prompt)
sys.stdout.flush()
line = sys.stdin.readline()[:-1]
if not line:
sys.exit()
if line in choices:
return line
print(repr(line), 'is not a valid choice.')
你可能想用str.translate()来处理这个:
sys.stdout.write(encode_map[char] if char in encode_map else char)
8
既然你提到了格式和风格，我很惊讶其他人还没有提到 PEP 8。这个文档主要是给那些想要被纳入标准库的模块提供指导，但我发现它的很多建议在其他地方也都适用。