EX6: Strings and Text

例子：

# 给 types_of_people 赋值：10
types_of_people = 10
# 将字符串赋值给 x ，使用 f-string 将 type_of_people 嵌入 x 中
x = f"There are {types_of_people} types of people."

# 赋值
binary = "binary"
do_not = "don't"
# 赋值并嵌入
y = f"Those who know {binary} and those who {do_not}."

# 打印输出
print(x)
print(y)

# 插入变量值打印输出
print(f"I said: {x}")
print(f"I also said: '{y}'")

# 赋值
hilarious = False
joke_evaluation = "Isn't that joke so funny?! {}"

print(joke_evaluation.format(hilarious))

w = "This is the left side of..."
e = "a string with a right side."

# 连接两个字符串组成更长的字符串
print(w + e)

学习内容：f；format；用print进行debug

f
  • 变量字符串格式化输出，将变量值融入句子中成为新的字符串输出
  • 会将变量值类型转化为字符串输出
  • f不能嵌套
  • 开头例子表明，f创建的新字符串可以赋值给变量
.format()
  • 格式化字符串的函数 str.format()，它增强了字符串格式化的功能
  • f 和.format()大部分时候可以互换
    输入：
hilarious = False
joke_evaluation1 = "Isn't that joke so funny?! {}"
joke_evaluation2 = "Isn't that joke so funny?! {}"

print(joke_evaluation1.format(hilarious))
print(joke_evaluation2 + f"{hilarious}")
print(f"{joke_evaluation2}" + f"{hilarious}")
print(f"{joke_evaluation2}{hilarious}")

结果：

Isn't that joke so funny?! False
Isn't that joke so funny?! False
Isn't that joke so funny?! False
Isn't that joke so funny?! False

从结果可以看出，f本身就能够存在很多种表达方式，且能与.format()进行互换。

用print进行debug
  • 找到可能出错的地方，可以在错误前一行和后一行用print输出，判断是否出错，或者是弄明白某段代码的含义。
  • 比如为了弄明白变量x的赋值内容：
    输入：
types_of_people = 10
x = f"There are {types_of_people} types of people."

binary = "binary"
do_not = "don't"
y1 = "Those who know {binary} and those who {do_not}."

print(">>>> after assign y : ", y1)
print(x)
print(">>>> before print y : ", y1)
print(y1)

结果：

>>>> after assign y :  Those who know {binary} and those who {do_not}.
There are 10 types of people.
>>>> before print y :  Those who know {binary} and those who {do_not}.
Those who know {binary} and those who {do_not}.

从结果可以看出y变量少了什么（等号后面应该还有一个f）

深入练习（Study Drills）

我认为共有3个地方是字符串套字符串的
y = f"Those who know {binary} and those who {do_not}."
print(f"I said: {x}")
print(f"I also said: '{y}'")

以下两个不是

x = f"There are {types_of_people} types of people."
print(joke_evaluation.format(hilarious))

原因是，下面的两条命令中，第一条是在字符串中嵌套了数值类型变量，第二条是字符串中嵌套了Boolean类型变量（true/false）。

改变代码（寻找可能情况及错误）

不同类型的数据不能用+连接

输入：

hilarious = False
joke_evaluation2 = "Isn't that joke so funny?! {}"

print(f"{joke_evaluation2 + hilarious}")

结果：

Traceback (most recent call last):
  File "TEST.py", line 4, in <module>
    print(f"{joke_evaluation2 + hilarious}")
TypeError: can only concatenate str (not "bool") to str

类型错误：只能连接同类型的变量值。

单引号和双引号的混合使用

输入：

print("把'单引号'放进双引号中")
print('把"双引号"放进单引号中')
print("把"另外双引号"放进双引号中")
print('把'另外单引号'放进单引号中')

结果：

把'单引号'放进双引号中
把"双引号"放进单引号中

  File "TEST.py", line 3
    print("把"另外双引号"放进双引号中")
                 ^
SyntaxError: invalid syntax

  File "TEST.py", line 4
    print('把'另外单引号'放进单引号中')
                 ^
SyntaxError: invalid syntax

从结果可以得知单引号和双引号可以混合使用，但是单引号中不可存在另外的单引号，双引号中不能存在另外的双引号。（以上结果为结果的合并，想要测试此错误要要分开测试）