Python: numeric types and string types of built-in method

A digital type built-in method

1.1 Integer built-in method

1. effect

   Description age, number, id number

2. Defined way

x = 10
x = int('10')
x = int(10.1)
x = int('10.1')  # 报错

3. Built-in method

   No built-in method, only the arithmetic and compare operations

4. A value or presence of a plurality of values

   Save a value

5. Orderly or disorderly orderly: the index; disorder: None Index

   Are they not say that

6. Variable or non-variable (Key)

   Digital type immutable

• Variable (variable value terms)

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lis = [1,2,3]
print(id(lis))
lis[0] = 2   #lis-->[2,2,3]
print(id(lis))

• Immutable (in terms of the value of the variable), the value becomes variable id

x = 10
print(id(x))
x = 20
print(id(x))

1.2 float built-in method

With integer

Second, the method of the built-in string type

2.1 Role

Name / gender / address

2.2 define how

s = b‘sdkfljl’   # 打印出来的bytes类型，二进制类型，010011001011001011

print(s)

print(‘中文’,encode(‘utf8’))

2.3 String built-in method (only string type to use)

s = ‘forever handsome’

Priority master (you must have to master today)

1. Index values

print(s[1])

2. Index sliced

print(s[4:0:1])  #  1 表示从左到右

print(s[-4:0:-1])   #  -1 表示从右到左

3. for loop

for i in s:

  print(i)

4. strip () specified character ends removed

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s1 = ‘              nick handsome          ’

print(s1.strip())    # 去除两端的空白
s2 = '****!!!nick handsome-----***'
print(s2.strip('-*!'))   # 指定多个字符一起去掉，只能strip里面有的字符就全部干掉

5. split () Cutting

print(s.split()) # 默认以空格为切割条件 
print(s.split('/')) # 以/切割 
print(s.split('!')) # 以！切割

6. in 或 not in

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print('forever' in s ) #True 
print('!' not in s) # True

7. Length len

  s = '123'
  print(len(s)) # 3 # 求字符串的长度

2.4 a stored value or a plurality of values

A value

2.5 orderly or disorderly

Ordered

2.6 variable or non-variable (Key)

Variable: The value of constant change id, not a hash

Immutable: variable id value becomes, hashable

Immutable

s2 = 'abc'
print(id(s2))
s2 += 'abc'
print(id(s2))