Python String find()用法及代碼示例

message = 'Python is a fun programming language'

# check the index of 'fun'
print(message.find('fun'))

# Output: 12

用法:

用法:

str.find(sub[, start[, end]] )

參數：

find() 方法最多接受三個參數：

• sub- 它是要在str String 。
• start和結尾(可選) - 範圍str[start:end]在其中搜索子字符串。

返回：

find() 方法返回一個整數值：

• 如果子字符串存在於字符串中，則返回子字符串第一次出現的索引。
• 如果字符串中不存在子字符串，則返回-1.

find() 方法的用法

示例 1：find() 沒有開始和結束參數

quote = 'Let it be, let it be, let it be'

# first occurance of 'let it'(case sensitive)
result = quote.find('let it')
print("Substring 'let it':", result)

# find returns -1 if substring not found
result = quote.find('small')
print("Substring 'small ':", result)

# How to use find()
if (quote.find('be,') != -1):
    print("Contains substring 'be,'")
else:
    print("Doesn't contain substring")

輸出

Substring 'let it': 11
Substring 'small ': -1
Contains substring 'be,'

示例 2：find() 帶有 start 和 end 參數

quote = 'Do small things with great love'

# Substring is searched in 'hings with great love'
print(quote.find('small things', 10))

# Substring is searched in ' small things with great love' 
print(quote.find('small things', 2))

# Substring is searched in 'hings with great lov'
print(quote.find('o small ', 10, -1))

# Substring is searched in 'll things with'
print(quote.find('things ', 6, 20))

輸出

-1
3
-1
9