Python3字串

var1 = 'Hello World!'
var2 = "Python Programming"

存取字串的值

#!/usr/bin/python3

var1 = 'Hello World!'
var2 = "Python Programming"

print ("var1[0]: ", var1[0])
print ("var2[1:5]: ", var2[1:5])

var1[0]:  H
var2[1:5]:  ytho

更新字串

可以通過(再)分配給另一個字串變數來「更新」現有的字串。新的值可以相關聯它之前的值或使用另一個完全不同的字串。例如 -

#!/usr/bin/python3

var1 = 'Hello World!'

print ("Updated String :- ", var1[:6] + 'Python')

Updated String :-  Hello Python

跳脫字元

字串特殊操作符

字串格式化操作

Python有一個最酷的功能是字串格式運算子%。這個操作符對於字串是是唯一的，並填補了 C語言中 printf()系列函式。下面是一個簡單的例子-

#!/usr/bin/python3

print ("My name is %s and weight is %d kg!" % ('Zara', 21)) 

My name is Zara and weight is 21 kg!

三重引號

#!/usr/bin/python3

para_str = """this is a long string that is made up of
several lines and non-printable characters such as
TAB ( \t ) and they will show up that way when displayed.
NEWLINEs within the string, whether explicitly given like
this within the brackets [ \n ], or just a NEWLINE within
the variable assignment will also show up.
"""
print (para_str) 

當執行上面的程式碼，它產生了以下結果。注意，如何每一個特殊字元已經轉換到它的列印形式，一直到最後的NEWLINE之間的字串的結尾關閉三重引號。還要注意的是出現新行或者使用一行或末尾明確回車其換碼(\ n)-

this is a long string that is made up of
several lines and non-printable characters such as
TAB (    ) and they will show up that way when displayed.
NEWLINEs within the string, whether explicitly given like
this within the brackets [
 ], or just a NEWLINE within
the variable assignment will also show up. 

原始字串不會把反斜槓作為一個特殊字元。 把一個原始字串中的每個字元保持原來編寫的方式 -

#!/usr/bin/python3
(
print ('C:\\nowhere')

C:\nowhere

#!/usr/bin/python3

print (r'C:\\nowhere')

C:\\nowhere

Unicode字串

在Python 3，所有的字串都是以Unicode表示。在Python2中內部儲存為8位元ASCII，因此，它需要附上「u」以讓明確使用的是Unicode。但在Python3 中現在不再是必要的。

字串內建的方法