Detailed explanation of python int() function examples

int(x, [base])

Function:

The function is to convert a number or base type string into an integer. (Python video tutorial)

Function prototype:

int(x=0)

int(x , base=10), the default value of base is 10, which means that when the value of base is not specified, the function will treat x as decimal.

Applicable Python version:

Python2.x

Python3.x

Note:

1. x can be a number or a string, but after base is assigned, x can only be a string

2. When x is used as a string, it must be of base type, that is to say When x becomes a number, it must be represented in base number

Python English documentation explanation:

class int(x=0)

class int(x, base=10)

Return an integer object constructed from a number or string x, or return 0 if no arguments are given. If x is a number, return x.__int__(). For floating point numbers, this truncates towards zero.

If x is not a number or if base is given, then x must be a string, bytes, or bytearray instance representing an integer literal in radix base. Optionally, the literal can be preceded by + or - (with no space in between) and surrounded by whitespace. A base-n literal consists of the digits 0 to n-1, with a to z ( or A to Z) having values ​​10 to 35. The default base is 10. The allowed values ​​are 0 and 2–36. Base-2, -8, and -16 literals can be optionally prefixed with 0b/0B, 0o/0O , or 0x/0X, as with integer literals in code. Base 0 means to interpret exactly as a code literal, so that the actual base is 2, 8, 10, or 16, and so that int('010', 0) is not legal, while int('010') is, as well as int('010', 8).

The integer type is described in Numeric Types — int , float, complex.

Changed in version 3.4: If base is not an instance of int and the base object has a base.__index__ method, that method is called to obtain an integer for the base. Previous versions used base.__int__ instead of base.__index__.

##Changed in version 3.6: Grouping digits with underscores as in code literals is allowed.

Code example:

1. When x is a number:

　　int(3.14)            # 3
　　int(2e2)             # 200
　　int(100, 2)          # 出错，base 被赋值后函数只接收字符串

2. When x is a string:

　　int('23', 16)      # 35
　　int('Pythontab', 8)      # 出错，Pythontab不是个8进制数

3. The possible value range of base is 2~36, including all English letters ( Case-insensitive), F in hexadecimal represents 15, then G will represent 16 in binary, and so on....Z represents 35 in hexadecimal

　　int('FZ', 16)      # 出错，FZ不能用十六进制表示
　　int('FZ', 36)      # 575

4. The string 0x can appear in hexadecimal and is regarded as a hexadecimal symbol. Similarly, 0b can appear in binary and is regarded as a number 0 and a letter. x

　　int('0x10', 16)  # 16，0x是十六进制的符号
　　int('0x10', 17)  # 出错，'0x10'中的 x 被视作英文字母 x
　　int('0x10', 36)  # 42804，36进制包含字母 x

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