Python字符计数器仅统计第一行，如何实现多行字符统计？

问题分析 #

• 多行读取失效问题：Python的input()函数设计为读取单行输入，遇到换行符就会终止读取，所以你输入多行内容时只能拿到第一行数据。
• 隐藏bug1：Python字符串为不可变类型，replace()方法不会修改原字符串，只会返回替换后的新字符串，你当前代码中的替换操作没有赋值回原变量，所有过滤规则完全不生效。
• 隐藏bug2：数学符号、括号、其他字符的三项判断条件错误引用了whatTo3Do变量，导致这三项的设置不会生效。

修复后的完整代码 #

import time
import sys

print("Please answer Y or N to the following questions:")
whatTo1Do = input("Would you like to include spaces in the character count? " )
whatTo2Do = input("Would you like to include commas in the character count? " )
whatTo3Do = input("Would you like to include apostrophes in the character count? " )
whatTo4Do = input("Would you like to include maths symbols (+, <, ÷, etc.) in the character count? " )
whatTo5Do = input("Would you like to include brackets in the character count? " )
whatTo6Do = input("Would you like to include other characters (~, `, \, %, &, etc.) in the character count? " )
yas = input("Your settings are displayed above. Are they correct? ")
if yas == "Y":
    pass
elif yas == "N":
    print("Please press OK to restart.")
    time.sleep(1)
    exit()
# 支持多行读取的输入逻辑
print("Enter your text here to count the characters based on your settings above: ")
print("(输入完成后：Windows系统按Ctrl+Z再按回车，macOS/Linux系统按Ctrl+D)")
text = sys.stdin.read()

# 修正替换逻辑与判断条件
if whatTo1Do.lower() in ("n", "no"):
    text = text.replace(" ", "")
if whatTo2Do.lower() in ("n", "no"):
    text = text.replace(",", "")
if whatTo3Do.lower() in ("n", "no"):
    text = text.replace("'", "").replace('"', "")
if whatTo4Do.lower() in ("n", "no"):
    for c in ("×", "÷", "=", "-", "+", ">", "<", "^", "*"):
        text = text.replace(c, "")
if whatTo5Do.lower() in ("n", "no"):
    for c in ("[", "]", "(", ")", "{", "}"):
        text = text.replace(c, "")
if whatTo6Do.lower() in ("n", "no"):
    for c in ("~", "`", "@", "#", "$", "%", "&", "\\", "|", "/"):
        text = text.replace(c, "")

print("There are", len(text), "characters in your text. (=")

改动说明 #

1. 引入sys模块，用sys.stdin.read()替代input()读取输入，会读取所有输入内容直到结束符，支持包含换行的多行内容。
2. 所有replace()操作的结果都赋值回text变量，替换逻辑生效。
3. 修正了4、5、6项设置的判断条件，同时用lower()统一转小写判断，简化了判断逻辑。
4. 把重复的replace操作改成循环遍历，代码更简洁易维护。
5. 修正了反斜杠字符的转义写法，避免转义错误。

内容的提问来源于stack exchange，提问作者red-back spider