笨辦法學Python – 習題8-10: Printing & Printing, Printing

無緣の邂逅#發表於2019-01-17
Python

目錄

1、習題 8: 列印，列印

學習目標：繼續學習 %r 的格式化輸出。

習題八中的練習程式碼是：

#! -*-coding=utf-8 -*-

formatter = "%r %r %r %r %r "

print formatter % (1, "hello", [1,2,3], (1,2,3), {"name":"jack"})

print formatter % ("one", "two", "three", "four", "five")

print formatter % (True, False, True, False, False)

print formatter % (
    "I had this thing. ",
    "That you could type up right. ",
    "But it didn`t sing. ",
    "So I said doognight. ",
    "Hello world."
)

上述程式碼的執行結果是：

C:Python27python.exe D:/pythoncode/stupid_way_study/demo8/Exer8-1.py
1 `hello` [1, 2, 3] (1, 2, 3) {`name`: `jack`} 
`one` `two` `three` `four` `five` 
True False True False False 
`I had this thing. ` `That you could type up right. ` "But it didn`t sing. " `So I said doognight. ` `Hello world.` 

Process finished with exit code 0

注意：上述程式碼說明兩個點，一個是%r 的作用，是佔位符，可以將後面給的值按原資料型別輸出(不會變)，支援數字、字串、列表、元組、字典等所有資料型別。

還有一個需要注意的就是程式碼的最後一行：

print formatter % (
    "I had this thing. ",
    "That you could type up right. ",
    "But it didn`t sing. ",
    "So I said doognight. ",
    "Hello world."
)
`I had this thing. ` `That you could type up right. ` "But it didn`t sing. " `So I said doognight. ` `Hello world.`

最後輸出的語句中既有單引號，也有雙引號。原因在於 %r 格式化字元後是顯示字元的原始資料。而字串的原始資料包含引號，所以我們看到其他字串被格式化後顯示單引號。 而這條雙引號的字串是因為原始字串中有了單引號，為避免字元意外截斷，python 自動為這段字串新增了雙引號。

2、習題 9: 列印，列印，列印

學習目標：瞭解
的含義

習題九中的練習程式碼是：

#! -*-coding=utf-8 -*-

days = "Mon Tue Wed Thu Fri Sat Sun"

months = "Jan
Feb
Mar
Apr
May
Jun
Jul
Aug"

print "Here are the days: ",days
print "Here are the months: ",months

print """
There`s something going on here.
With the three double-quotes.
We`ll be able to type as much as we like.
Even 4 lines if we want, or 5, or 6.
"""
C:Python27python.exe D:/pythoncode/stupid_way_study/demo9/Exer9-1.py
Here are the days:  Mon Tue Wed Thu Fri Sat Sun
Here are the months:  Jan
Feb
Mar
Apr
May
Jun
Jul
Aug

There`s something going on here.
With the three double-quotes.
We`ll be able to type as much as we like.
Even 4 lines if we want, or 5, or 6.

Process finished with exit code 0

上述程式碼有兩個點需要注意下，一個是換行符
,一個是註釋符三引號。換行符就是避免程式碼過長影響閱讀性而手動進行程式碼換行操作，
其實只是一個字元，類似的還有製表符 ，具體的更過的換行符知識請見下一題。

3、習題 10: 那是什麼？

學習目標：瞭解
的含義，瞭解   的含義

首先來了解一下兩種讓字串擴充套件到多行的方法：

  1. 換行符
    (back-slash n )：兩個字元的作用是在該位置上放入一個“新行(new line)”字元
  2. 雙反斜槓(double back-slash)   ：這兩個字元組合會列印出一個反斜槓來

3.1、轉義序列：

下面介紹下再Python中常見的轉義序列：

轉義字元 描述
 (在行尾時) 續行符
  反斜槓符號
` 單引號
“ 雙引號
a 響鈴
退格(Backspace)
e 轉義

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