5.a字符串类型内置方法
字符串类型内置方法
优先掌握(*****)
- 按索引取值
- 切片
- 长度len
- 成员运算in|not in
- 移除空白strip
- 切分split
- 循环
1.按索引取值（只可取不可改变）
# str索引取值
msg = 'hello nick'
# 0123456789 # 索引序号
print(f'索引为6: {msg[6]}')
print(f'索引为-3: {msg[-3]}')
索引为6: n
索引为-3: i
2.切片（顾头不顾尾，步长）
# 索引切片
msg = 'hello nick'
# 0123456789 # 索引序号
print(f'切片3-最后: {msg[3:]}')
print(f'切片3-8: {msg[3:8]}')
print(f'切片3-8，步长为2: {msg[3:8:2]}')
print(f'切片3-最后，步长为2: {msg[3::2]}')
# 了解，步长为正从左到右；步长为负从右到左
print('\n**了解知识点**')
print(f'切片所有: {msg[:]}')
print(f'反转所有: {msg[::-1]}')
print(f'切片-5--2: {msg[-5:-2:1]}')
print(f'切片-2--5: {msg[-2:-5:-1]}')
切片3-最后: lo nick
切片3-8: lo ni
切片3-8，步长为2: l i
切片3-最后，步长为2: l ik
**了解知识点**
切片所有: hello nick
反转所有: kcin olleh
切片-5--2: ni
切片-2--5: cin
3.长度len
# str长度
msg = 'hello nick'
print(len(msg))
10
4.成员运算in和not in
# str成员运算
msg = 'my name is nick, nick handsome'
print(f"'nick' in msg: {'nick' in msg}")
print(f"'jason' not in msg: {'jason' not in msg}")
print(f"not 'jason' in msg: {not 'jason' in msg}")
'nick' in msg: True
'jason' not in msg: True
not 'jason' in msg: True
5.移除空白strip()
# str移除空白strip()
name = '&&&n ick'
print(f"name.strip('&'): {name.strip('&')}") # strip()默认为‘ ’，并且不修改原值，新创建空间
print(f"name: {name}")
# strip()应用场景
pwd = input('password: ') # 用户可能会手抖输入空格
if pwd.strip() == '123':
print('密码输入成功')
print(f"'*-& nick+'.strip('*-& +'): {'*-& nick+'.strip('*-& +')}")
name.strip('&'): n ick
name: &&&n ick
password: 123
密码输入成功
'*-& nick+'.strip('*-& +'): nick
6.切分split
# str切分split
info = 'nick:male:19'
info_list1 = info.split(':')
info_list2 = info.split(':', 1)
print(f'info_list1:{info_list1}')
print(f'info_list2:{info_list2}')
info_list1:['nick', 'male', '19']
info_list2:['nick', 'male:19']
7.循环
msg = 'hello nick'
for i in msg:
print(i)
h
e
l
l
o
n
i
c
k
需要掌握(****)
- lstrip&rstrip
- lower&upper
- startswith&endswith
- rsplit
- join
- replace
- isdigit
1.lstrip()和rstrip()
# str之lstrip()和rstrip()
name = '&&nick&&'
print(f"nick.lstrip('&'): {name.lstrip('&')}")
print(f"nick.rstrip('&'): {name.rstrip('&')}")
nick.lstrip('&'): nick&&
nick.rstrip('&'): &&nick
2.lower()和upper()
# str之lower()和upper()
name = 'Nick Chen'
print(f"name.upper(): {name.lower()}")
print(f"name.upper(): {name.upper()}")
name.upper(): nick chen
name.upper(): NICK CHEN
3.startswith()和endswith()
# str之startswith()和endswith()
name = 'Nick Chen'
print(f"name.startswith('Nick'): {name.startswith('Nick')}")
print(f"name.endswith('chen'): {name.endswith('chen')}")
name.startswith('Nick'): True
name.endswith('chen'): False
4.rsplit()
# str之rsplit()
info = 'nick:male:19'
print(f"info.rsplit(':', 1): {info.rsplit(':', 1)}") # 从右开始切割
info.rsplit(':', 1): ['nick:male', '19']
5.join()
lis = [1,2,'19']
print(f"':'.join(lis): {':'.join(lis)}") # 报错，数字不可和字符串拼接
# str之join()
lis = ['nick', 'male', '19']
print(f"':'.join(lis): {':'.join(lis)}")
':'.join(lis): nick:male:19
6.replace()
# str值replace()
name = 'nick shuai'
print(f"name.replace('shuai','handsome'): {name.replace('shuai','handsome')}")
name.replace('shuai','handsome'): nick handsome
7.isdigit()
# str值isdigit()
salary = '111'
print(salary.isdigit()) # True
salary = '111.1'
print(salary.isdigit()) # False
True
False
# str之isdigit()应用场景
age = input('age: ')
if age.isdigit():
age = int(age)
if age < 18:
print('小姐姐')
else:
print('阿姨好')
else:
print(f'你的年龄能是这个{age}?')
age: 逗你玩？
你的年龄能是这个逗你玩？?
其他操作(**)
- find|rfind|index|rindex|count
- center|ljust|rjust|zfill
- expandtabs
- captalize|swapcase|title
- is系列
1.find()、rfind()、index()、rindex()、count()
# str之find()、rfind()、index()、rindex()、count()
msg = 'my name is tank, tank shi sb, hha'
print(f"msg.find('tank'): {msg.find('tank')}") # 找不到返回-1
print(f"msg.find('tank',0,3): {msg.find('tank',0,3)}")
print(f"msg.rfind('tank'): {msg.rfind('tank')}") # 找不到返回-1
print(f"msg.index('tank'): {msg.index('tank')}") # 找不到报错
print(f"msg.rindex('tank'): {msg.rindex('tank')}") # 找不到报错
print(f"msg.count('tank'): {msg.count('tank')}")
msg.find('tank'): 11
msg.find('tank',0,3): -1
msg.rfind('tank'): 17
msg.index('tank'): 11
msg.rindex('tank'): 17
msg.count('tank'): 2
2.center()、ljust()、rjust()、zfill()
# str之center()、ljust()、rjust()、zfill()
print(f"'info nick'.center(50,'*'): {'info nick'.center(50,'*')}")
print(f"'info nick'.ljust(50,'*'): {'info nick'.ljust(50,'*')}")
print(f"'info nick'.rjust(50,'*'): {'info nick'.rjust(50,'*')}")
print(f"'info nick'.zfill(50): {'info nick'.zfill(50)}") # 默认用0填充
'info nick'.center(50,'*'): ********************info nick*********************
'info nick'.ljust(50,'*'): info nick*****************************************
'info nick'.rjust(50,'*'): *****************************************info nick
'info nick'.zfill(50): 00000000000000000000000000000000000000000info nick
3.expandtabs()
# str之expandtabs()
print("a\\tb\\tc: %s"%('a\tb\tc\t')) # 默认制表符8个空格
print("'a\\tb\\tc'.expandtabs(32): %s"%('a\tb\tc\t'.expandtabs(32)))
a\tb\tc: a b c
'a\tb\tc'.expandtabs(32): a b c
4.captalize()、swapcase()、title()
# str之captalize()、swapcase()、title()
name = 'nick handsome sWAPCASE'
print(f"name.capitalize(): {name.capitalize()}")
print(f"name.swapcase(): {name.swapcase()}") # 大小写互转
print(f"name.title(): {name.title()}")
name.capitalize(): Nick handsome swapcase
name.swapcase(): NICK HANDSOME Swapcase
name.title(): Nick Handsome Swapcase
