python经典案例:查找字符串（python中查找字符串）

问题：查找字符串

1.使用in关键字查找字符串

#!/usr/bin/python
#coding:utf-8
#author:菜就多练呀
text = "Hello, welcome to my world."
search_string = "welcome"

if search_string in text:
    print("找到字符串！")#找到字符串！
else:
    print("未找到字符串！")

2.使用字符串的find()方法

#!/usr/bin/python
#coding:utf-8
#author:菜就多练呀
text = "Hello, welcome to my world."
search_string = "welcome"

position = text.find(search_string)

if position != -1:
    print("找到字符串！")
    print("位置：", position)
else:
    print("未找到字符串！")

输出结果：

找到字符串！
位置： 7

3.使用正则表达式

#!/usr/bin/python
#coding:utf-8
#author:菜就多练呀
import re
text = "Hello, welcome to my world."
search_string = "welcome"
pattern = re.compile(search_string)
if pattern.search(text):
    print("找到字符串！")#找到字符串！
else:
    print("未找到字符串！")

4.使用count()方法查找字符串

#!/usr/bin/python
#coding:utf-8
#author:菜就多练呀
text = "Hello, welcome to my world. Welcome to our world."
search_string = "welcome"
count = text.count(search_string)
print("字符串 'welcome' 出现的次数：", count)#字符串 'welcome' 出现的次数： 1

5.使用 split() 方法查找字符串

#author:菜就多练呀
text = "Hello, welcome to my world."
search_string = "welcome"
words = text.split()
for word in words:
    if word == search_string:
        print("找到字符串！")
        break
else:
    print("未找到字符串！")

注意：使用split()方法，一定要注意标点符号。如果查找world时，结果为未找到字符串。因为split()方法的结果为:['Hello,', 'welcome', 'to', 'my', 'world.']

如果想去掉标点符号，可以使用下面方法：

def remove_punctuation(word):
    return word.replace(",", "").replace("!", "").replace("?", "")
my_list = ["Hello,", "welcome", "to", "my", "world!"]
no_punctuation_list = [remove_punctuation(word) for word in my_list]
print(no_punctuation_list)

输出结果：

['Hello', 'welcome', 'to', 'my', 'world']