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：
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<len(txt):
if txt[start:end] == key:
if start == 0:
print("Starts with",key)
break
start+=1
end+=1
else:
print('Not Contains')
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
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