int(x, [base])

功能：

函數(shù)的作用是將一個(gè)數(shù)字或base類型的字符串轉(zhuǎn)換成整數(shù)。

函數(shù)原型：

int(x=0)
int(x, base=10)，base缺省值為10，也就是說不指定base的值時(shí)，函數(shù)將x按十進(jìn)制處理。

適用Python版本：

Python2.x
Python3.x

注意：

1. x 可以是數(shù)字或字符串，但是base被賦值后 x 只能是字符串
2. x 作為字符串時(shí)必須是 base 類型，也就是說 x 變成數(shù)字時(shí)必須能用 base 進(jìn)制表示

Python英文文檔解釋：

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.

代碼實(shí)例：

1. x 是數(shù)字的情況：

int(3.14)      # 3
int(2e2)       # 200
int(100, 2)     # 出錯(cuò)，base 被賦值后函數(shù)只接收字符串

2. x 是字符串的情況：

int('23', 16)   # 35
int('Pythontab', 8)   # 出錯(cuò)，Pythontab不是個(gè)8進(jìn)制數(shù)

3. base 可取值范圍是 2~36，囊括了所有的英文字母(不區(qū)分大小寫)，十六進(jìn)制中F表示15，那么G將在二十進(jìn)制中表示16，依此類推....Z在三十六進(jìn)制中表示35

int('FZ', 16)   # 出錯(cuò)，F(xiàn)Z不能用十六進(jìn)制表示
int('FZ', 36)   # 575

4. 字符串 0x 可以出現(xiàn)在十六進(jìn)制中，視作十六進(jìn)制的符號(hào)，同理 0b 可以出現(xiàn)在二進(jìn)制中，除此之外視作數(shù)字 0 和字母 x

int('0x10', 16) # 16，0x是十六進(jìn)制的符號(hào)
int('0x10', 17) # 出錯(cuò)，'0x10'中的 x 被視作英文字母 x
int('0x10', 36) # 42804，36進(jìn)制包含字母 x

總結(jié)

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