1.编写一个程序来检查给定的密钥是否可用：
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)
break
start+=1
end+=1
else:
print('not contains')
contains fruit
2.编写一个程序来查找给定的关键位置：
find() 返回找到它的位置。
txt = "python is my favourite language"
key = 'python'
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')
contains python 0 5
3.编写程序检查以指定键开头的单词：
startswith() 检查字符串是否以指定值开头。
txt = "python is my favourite language"
key = 'python'
l = len(key)
start = 0
end = l
while end<=len(txt):
if txt[start:end] == key:
if start==0:
print("starts with", key)
break
start+=1
end+=1
else:
print('not contains')
starts with python
检查以指定键开头的单词的另一种方法：
txt = "apples are good, apple is my favorite fruit"
key = 'apple'
l = len(key)
if txt[0:l]==key:
print('starts with',key)
starts with apple
4.编写程序检查以指定键结尾的单词：
endswith() 检查字符串是否以指定值结尾。
txt = "my favourite language is python"
key = 'python'
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 contains')
ends with python
检查单词以指定键结尾的另一种方法：
txt = "apples are good, apple is my favorite fruit"
key = 'fruit'
l = len(key)
if txt[-l:]==key:
print('ends with',key)
ends with fruit
5.编写一个程序来检查给定的单词是否为字母：
isalpha() 检查字符串中的所有字符都是字母。
alpha = 'abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz'
word = 'abcdefgh'
for letter in word:
if letter not in alpha:
print('not all are alphabets')
break
else:
print('all are alphabets')
all are alphabets
6.编写一个程序来检查给定的单词是否为alnum：
isalnum() 检查字符串中的所有字符都是字母数字。
alpha = '0123456789abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz'
word = 'pritha017@gmail.com'
for letter in word:
if letter not in alpha:
print('not all are alphabets and numbers')
break
else:
print('all are alphabets and numbers')
not all are alphabets and numbers
7.编写一个程序来检查给定的单词是否小写：
islower() 检查字符串中的所有字符均为小写。
alpha = 'abcdefghijklmnopqrstuvwxyz'
word = 'lakshmipritha'
for letter in word:
if letter not in alpha:
print('not all are lowercase alphabets')
break
else:
print('all are lowercase alphabets')
all are lowercase alphabets
8.编写一个程序来检查给定的单词是否大写：
isupper() 检查字符串中的所有字符均为大写。
alpha = 'abcdefghijklmnopqrstuvwxyz'
word = 'lakshmipritha'
for letter in word:
if letter not in alpha:
print('not all are uppercase alphabets')
break
else:
print('all are uppercase alphabets')
all are uppercase alphabets
9.编写一个程序来检查空间是否可用：
isspace() 检查文本中的空格。
word = ' '
for letter in word:
if letter != ' ':
print("not all are spaces")
break
else:
print('all are spaces')
all are spaces
任务：
1.编写一个将大写字母转换为小写字母的程序：
lower() 将字符串转换为小写。
txt = "hello, and welcome to my world!"
for letter in txt:
if letter>='a' and letter<'z':
letter = ord(letter)+32
letter = chr(letter)
print(letter,end='')
hello, and welcome to my world!
2.编写一个将小写字母转换为大写字母的程序：
upper() 将字符串转换为大写。
txt = "hello, and welcome to my world!"
for letter in txt:
if letter>='a' and letter<'z':
letter = ord(letter)-32
letter = chr(letter)
print(letter,end='')
hello, and welcome to my world!
3.编写一个程序来检查给定的字符串标题是否：
istitle() 检查字符串是否遵循标题规则。
