python转换成无符号 python 无符号数

python实现无符号数识别

无符号数识别状态图为：

# -*- coding: utf-8 -*-
"""
Created on Sat Apr  4 16:06:51 2020

@author: 侯
"""

# * 状态有
# * -1: end_state
# * 0 :
# *   读取 数字      -> 1
# *   读取 'e'       -> 3
# *
# * 1 :
# *   读取 数字      -> 1
# *   读取 '.'       -> 2
# *   读取 'E'或'e'  -> 4
# * 2 :
# *   读取 数字      -> 2
# *   读取 'E'或'e'  -> 4
# * 3:
# *   读取 数字      -> 2
# * 4:
# *   读取 +/-       -> 5
# *   读取 数字      -> 6
# * 5:
# *   读取 数字      -> 6
# * 6:
# *   读取 数字      -> 6


#验证s是否为无符号实数
def Test(s):
    #digit代表数字
    digit=['0','1','2','3','4','5','6','7','8','9']
    result=''#识别结果
    power=''#指数幂
    start_state=0#开始状态为0
    end_state=-1#结束状态设为-1
    for i in range(len(s)):
        if start_state==0:#开始状态为0
            if s[i]=='.':#读取的字符是'.'时，进入状态3
                start_state=3
                result=result+'0'+s[i]
            elif s[i] in digit:#读取的字符是数字时，进入状态1
                start_state=1
                result=result+s[i]
            else:
                start_state=-1
                break
        elif start_state==1:#开始状态为1
            if s[i] in digit:#读取的字符是数字时，进入状态1
                start_state=1
                result=result+s[i]
            elif s[i]=='.':#读取的字符是'.'时，进入状态2
                start_state=2
                result=result+s[i]
            elif s[i]=='E' or s[i]=='e':#读取的字符是'E'或'e'时，进入状态4
                start_state=4
            else:
                start_state=-1
                break
        elif start_state==2:#开始状态为2
            if s[i] in digit:#读取的字符是数字时，进入状态2
                start_state=2
                result=result+s[i]
            elif s[i]=='E' or s[i]=='e':#读取的字符是'E'或'e'时，进入状态4
                start_state=4
            else:
                start_state=-1
                break
        elif start_state==3:#开始状态为3
            if s[i] in digit:#读取的字符是数字时，进入状态2
                start_state=2
                result=result+s[i]
            else:
                start_state=-1
                break
        elif start_state==4:#开始状态为4
            if s[i]=='+' or s[i]=='-':#读取的字符是'+'或'-'时，进入状态5
                start_state=5
                power=power+s[i]
            elif s[i] in digit:#读取的字符是数字时，进入状态6
                start_state=6
                power=power+s[i]
            else:
                start_state=-1
                break
        elif start_state==5:#开始状态为5
            if s[i] in digit:#读取的字符是数字时，进入状态6
                start_state=6
                power=power+s[i]
            else:
                start_state=-1
                break
        elif start_state==6:#开始状态为6
            if s[i] in digit:#读取的字符是数字时，进入状态6
                start_state=6
                power=power+s[i]
            else:
                start_state=-1
                break
    if start_state==end_state or s=='.':
        print(s+"不是无符号实数")
    else:
        if power!='':
            result=str(float(result)*(10**int(power)))
        print(s+"   是   "+result)
if __name__=='__main__':
    test=['123','12.3','.123','123.','.','123e4',
          '456E3','1.23e+4','8.9E+2','.123e-4',
          '.34E-4','123.e4','123.e+4','123.e-4',
          '623.E-4','31*54','bfg','12a','a3','1..3']
    for i in range(len(test)):
        Test(test[i])

运行结果如下图所示：