Python Day-String 使用循环函数逻辑，任务

1) find(): 在字符串中搜索指定值并返回找到它的位置。

txt = "i love many fruits, apple is my favorite fruit"
key = 'fruit'
l = len(key)
start = 0 
end = l
while end<=len(txt):
    if txt[start:end] == key:
        print('contains', key)
        print(start, end-1)
        break
    start+=1
    end+=1
else:
    print('not contains')

输出：

LobeHub

LobeChat brings you the best user experience of ChatGPT, OLLaMA, Gemini, Claude

下载

contains fruit
12 16

2)startswith():如果字符串以指定值开头，则返回 true

示例：1

#starts with: 
txt = "python is my favourite language"
key = 'python'
l = len(key)
start = 0 
end = l
while end



输出：


starts with python





示例：2


txt = "apples are good, apple is my favorite fruit"
key = 'apple'
#starts with
l = len(key) #5
if txt[0:l] == key:
    print('starts with',key)




输出：


starts with apple




3)endswith():如果字符串以指定值结尾，则返回 true。

示例：1


txt = "apples are good, apple is my favorite fruit"
key = 'fruit'
#starts with
l = len(key) #5
if txt[-len(key):] == key:
    print('ends with',key)




输出：


ends with fruit




示例：2


txt = "python is my favourite language"
key = 'language'
l = len(key)
start = 0 
end = l
while end<=len(txt):
    if txt[start:end] == key:
        if end==len(txt):
            print("ends with",key)
        break
    start+=1
    end+=1
else:
    print('not ending with language')




输出：


ends with language




4) isalpha(): 如果字符串中的所有字符都在字母表中，则返回 true。

方法：1


word = 'abcdefgh'
for letter in word:
    if letter>='a' and letter<='z' or letter>='a' and letter<='z':
        continue
    else:
        print('not all are alphabets')
        break
else:
    print('all are alphabets')




方法：2


alpha = 'abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz'
word = 'abcdefgh'
for letter in word:
    if letter not in alpha:
        print('not all are alphabets')
        break
else:
    print('all are alphabets')




输出：


all are alphabets




5) isalnum(): 如果字符串中的所有字符都是字母数字，则返回 true。


#isalnum
alpha = '0123456789abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz'
word = 'abcd1234'
for letter in word:
    if letter not in alpha:
        print('not all are alphabets and numbers')
        break
else:
    print('all are alphabets and numbers')




输出：


all are alphabets and numbers




6) islower(): 如果字符串中的所有字符均为小写，则返回 true。


#islower
alpha = 'abcdefghijklmnopqrstuvwxyz'
word = 'lakshmipritha'
for letter in word:
    if letter not in alpha:
        print('not all are lower alphabets')
        break
else:
    print('all are lower alphabets')




输出：


all are lower alphabets




7) isupper(): 如果字符串中的所有字符均为大写，则返回 true。


#isupper
alpha = 'abcdefghijklmnopqrstuvwxyz'
word = 'guru'
for letter in word:
    if letter not in alpha:
        print('not all are uppercase alphabets')
        break
else:
    print('all are uppercase alphabets')




输出：


all are uppercase alphabets




8) isspace(): 如果字符串中的所有字符都是空格，则返回 true。


#isspace

word = '        '
for letter in word:
    if letter != ' ':
        print("not all are spaces")
        break
else:
    print('all are spaces')




输出：


all are spaces




任务：
1) lower(): 将字符串转换为小写。


txt = "python is my favourite language"
for letter in txt:
    if letter>='a' and letter<='z':
        letter = ord(letter)+32
        letter = chr(letter)
    print(letter,end='')




输出：


python is my favourite language




2) upper(): 将字符串转换为大写。


txt = "python is my favourite language"
for letter in txt:
    if letter>='a' and letter<='z':
        letter = ord(letter)-32
        letter = chr(letter)
    print(letter,end='')




输出：


python is my favourite language