Python数据类型之String字符串实例详解

print('I\'m \"ok\"')

>>>print('I\'m ok.')
I'm ok.
>>>print('I\'m learning\n python.')
I'm leanring
Python.
>>> print('\\\n\\')
\
\

>>> print('\\\t\\')
\  \
>>>print(r'\\\t\\')
\\\t\\

>>> print('''line1
  line2
  line3''')
line1
line2
line3

str1 = "hello world"
str2 = 'you are good'

#字符串的连接，通过"+"进行连接
s1 = 'welcome '
s2 = 'to guangzhou'
print(s1 + s2)

s1 = 'hello'
s2 = 'world'
print(s1, s2)
#使用"，"连接的时候，在"，"的位置会产生一个空格

s1 = 'hello'
s2 = 'world'
print("%s %s"%(s1, s2))

s1 = ['hello', 'world']
print("".join(s1))
print("*".join(s1))

#重复输出字符串，通过乘法的方式实现
s3 = 'good'
print(s3 * 3)

#通过索引的方式实现
#索引：给一个字符串中的字符从0开始编号，也称为下标
#索引的取值范围：[0，len(str)-1]
#访问方式： 变量名称[索引]
str3 = 'good'
print(str3[0])
#索引值还可以从-1开始，-1代表倒数第一个字符
print(str3[-1])

# 通过下标截取字符串
str1 = "hello world"
print(str1[3:6])
#注意：截取字符串的范围是str[start : end] 它是一个前闭后开的区间[start，end)
#如果n的值超过了字符串的最大长度，则仍然截取原下标的长度
#从开头截取到指定索引之前[0，5）
print(str1[:5])
#从指定截取到结尾[4,len(str1))
print(str1[4:])
#注意在使用str[start : end]来截取字符串的时候，若start不写默认从第一个字符开始
#若end不写，则默认到最后一个字符结束。取头去尾。
print("012345"[1:-1])

#判断字符串中是否包含某指定字符串
str4 = "you are a good boy"
print("good" in str4)
#若包含有则返回True否则为False

#通过%来改变后面的字母或者是符号的含义，%被称为占位符
# %s：格式化字符串
# %d：格式化整数
# %f：格式化浮点数，可指定小数点后的精度
age = 18
name = "丽丽"
weight = 45.5
print("my name is %s , I am %d year old and my weight is %.2f kg"%(name, age, weight))
#注意：%.nf表示精确到小数点后n位，会四舍五入

>>>num1 = eval('123')
>>>print(num1)
123
>>>num2 = eval("[1, 2, 3]")
>>>print(num2)
[1, 2, 3]
>>> num3 = eval("12-3")
>>> print(num3)
9

>>> len("you are good")
12

>>> str = "Hello World"
>>> print(str.lower())
hello world

>>> str = "Hello World"
>>> print(str.upper())
HELLO WORLD

>>> str = "Hello World"
>>> print(str.swapcase())
hELLO wORLD

>>> str = "Hello World"
>>> print(str.capitalize())
Hello world

>>> str = "Hello World"
>>> print(str.title())
Hello World

>>> str = "Hello World"
>>> print(str.center(50,"*"))
*******************Hello World********************

>>> str = "Hello World"
>>> print(str.ljust(50,"*"))
Hello World***************************************

>>> str = "Hello World"
>>> print(str.rjust(50,"*"))
***************************************Hello World

>>> str = "Hello World"
>>> print(str.zfill(50))
000000000000000000000000000000000000000Hello World

>>> str = "Hello World"
>>> print(str.count("hello", 0 , 10))
0

>>> str = "Hello World"
>>> str1 = "llo"
>>> print(str.find(str1, 0 , 10))
2

>>> str = "Hello World"
>>> str1 = "llo"
>>> print(str.rfind(str1, 0 , 10))
2

>>> str2 = "Hello World"
>>> str1 = "hello"
>>> print(str2.index(str1, 0 , 10))
ValueError: substring not found

>>> str = '**** you are very good'
>>> print(str.lstrip())
>>> print(str.lstrip())
**** you are very good
>>> print(str.lstrip("*"))
 you are very good

>>> str = '**** you are good****'
>>> print(str.rstrip())
**** you are good****
>>> print(str.rstrip("*"))
**** you are good

str1 = "*nih*a*o*"
print(str1.strip('*'))

>>> str1 = "hello you are good"
>>> str1.split()
['hello', 'you', 'are', 'good']
>>> str1.split(" ",2)
['hello', 'you', 'are good ']

str2 = '''how are
you ?
i am
fine
!
'''
list2 = str2.splitlines()
print(list2)

str2 = '''how are
you ?
i am
fine
!
'''
list2 = str2.splitlines(keepends=True)
print(list2)

list2 = ['you', 'are', 'very', 'great', '!']
str3 = ' '.join(list2)
print(str3)

str1 = "how are you , i am fine thank you"
str3 = "*".join(str1)
print(str3)

str1 = "how are you , i am fine thank you"
print(max(str1))

str1 = "how are you , i am fine thank you"
print(min(str1))

str1 = "how are you , i am fine thank you"
str2 = str1.replace("you" ,'me')
print(str2)

str5 = ""
dic = str5.maketrans("ac", "21")
# a--2  c--1
str7 = "how are you ,u ewe c "
print(str7.translate(dic))

str1 = "aaa bbb ccc deee"
print(str1.startswith("aa"))
str1 = "aaa bbb ccc deee"
print(str1.startswith("aa", 3, 9))

str1 = "aaa bbb ccc deee"
print(str1.endswith("deee"))
str1 = "aaa bbb ccc deee"
print(str1.endswith("e", 3 ,9))

str1 = "你好吗？"
data = str1.encode()
print(data)
print(type(data))

str1 = "你好吗？"
data = str1.encode()
print(data)
print(type(data))
data2 = data.decode()
print(data2)
print(type(data2))

str8 = "hello ni hao "
print(str8.isalpha())
str9 = "你好"
print(str9.isalpha())

str9 = '1234你好'
str10 = "sc22xdcd"
str11 = "ss1 2dd"
print(str9.isalnum())
print(str10.isalpha())
print(str11.isalnum())

str10 = "AA2221 你111"
print(str10.isupper())
str10 = "AAaaa"
print(str10.isupper())

str10 = "aa2221 你111"
print(str10.islower())

str1 = "Hello World"
print(str1.istitle())

print("123".isdigit())
print("123a".isdigit())

print("123一".isnumeric())
print("123a".isnumeric())

print("123".isdecimal())
print("123z".isdecimal())

print(" ".isspace())
print("\t".isspace())
print("\n".isspace())
print("\r".isspace())
print(" qq".isspace())

print(ord("A"))
print(ord("你"))

print(chr(68))
print(chr(20190))