Novice: one STR float-CodePudding

Just touch Python for three days, see the tutorial have a practice "of map and reduce. Write a str2float function, put the string '123.456' converts floating-point number 123.456"
Here is my code:

 
The from functools import reduce 
Def str2float (f) : 
Def to_float (x) : 
Df={' 1 ', 1, '2', 2, '3', 3 '4', 4, '5, 5,' 6 ', 6, '7', 7 '8', 8, '9, 9,' 0 ': 0} 
Return df [x] 

Def c10 (x, y=0) : 
Return * 10 x + y 

Def d10 (z, k) : 
* 0.1 * 0.1 m=z + k 
Return m 

D=0 
For s in f: 
If s==': 
I_=f [: d] 
F_=f/d + 1: 
F_='0' + f_] [: : - 1 

D=d + 1 

Ii=the reduce (c10, map (to_float, i_)) 
Ff=the reduce (d10, map (to_float, f_)) 
Return ii + ff

Results:
Python 3.7.3 (default, Apr 3, 2019, 05:39:12)
[GCC 8.3.0] on Linux
Type "help", "copyright", "credits" or "license" for more information.
> The from one import str2float
> Str2float (' 101.123 ')
101.123 & lt; - a normal
> Str2float (' 0.123 ')
0.12300000000000001 & lt; - the abnormal
> Str2float (' 1.123 ')
1.123
> Str2float (' 1.00123 ')
1.00123
> Str2float (' 0.00123 ')
0.0012300000000000002 & lt; - the abnormal
>

This is where the wrong?
Also, this code and a better writing?
Thank you very much!

CodePudding user response:

refer to the original poster XHFBX response:

just touch Python for three days, see the tutorial has a practice of "use of map and reduce. Write a str2float function, put the string '123.456' converts floating-point number 123.456"
Here is my code:
 
The from functools import reduce 
Def str2float (f) : 
Def to_float (x) : 
Df={' 1 ', 1, '2', 2, '3', 3 '4', 4, '5, 5,' 6 ', 6, '7', 7 '8', 8, '9, 9,' 0 ': 0} 
Return df [x] 

Def c10 (x, y=0) : 
Return * 10 x + y 

Def d10 (z, k) : 
* 0.1 * 0.1 m=z + k 
Return m 

D=0 
For s in f: 
If s==': 
I_=f [: d] 
F_=f/d + 1: 
F_='0' + f_] [: : - 1 

D=d + 1 

Ii=the reduce (c10, map (to_float, i_)) 
Ff=the reduce (d10, map (to_float, f_)) 
Return ii + ff 
Results:
Python 3.7.3 (default, Apr 3, 2019, 05:39:12)
[GCC 8.3.0] on Linux
Type "help", "copyright", "credits" or "license" for more information.
> The from one import str2float
> Str2float (' 101.123 ')
101.123 & lt; - a normal
> Str2float (' 0.123 ')
0.12300000000000001 & lt; - the abnormal
> Str2float (' 1.123 ')
1.123
> Str2float (' 1.00123 ')
1.00123
> Str2float (' 0.00123 ')
0.0012300000000000002 & lt; - the abnormal
>

This is where the wrong?
Also, this code and a better writing?
Thank you very much!

This is a bug, Python can't eliminate

CodePudding user response:

Direct a Decimal is good,

CodePudding user response:

There is no need to bother, itself comes with such a python function, num is output decimal

 
The from decimal import * 
S='1.231' 
Num=Decimal (s) 
Print (type (num))

CodePudding user response:

1. Directly using the float function:

 print (float (' 123.45 '))

2. Directly using the eval function:

 print (eval () '123.45')

3. Be sure to practice using the reduce and map can also ah, it feels a bit like its kill chickens:

 the from functools import reduce 
Def str2float (f) : 
S=f.s plit (') 
S1=list (s [0]) 
[1] s2=list (s) 
S2. Reverse () 
S2. Append (' 0 ') 
To_digit=lambda x: int (x) 
C10=lambda x, y: * 10 x + y 
D10=lambda x, y: * 0.1 x + y 
Ii=the reduce (c10, map (to_digit, s1)) 
Ff=the reduce (d10, map (to_digit, s2)) 
Return ii + ff 
Print (str2float (' 123.45 '))

CodePudding user response:

The problem is the accuracy of float

Single-precision floating-point decimal only six more accuracy

CodePudding user response:

The from functools import reduce
The from decimal import decimal

S=input (' please input string:)

Def str2float (f) :
Def to_float (x) :
Df={' 1 ', 1, '2', 2, '3', 3 '4', 4, '5, 5,' 6 ', 6, '7', 7 '8', 8, '9, 9,' 0 ': 0}
Return df [x]

Def c10 (x, y=0) :
Return * 10 x + y

Def d10 (z, k) :
Tmp1=Decimal (STR) (z) * Decimal (STR (0.1))
Tmp2=Decimal (STR) (k) * Decimal (STR (0.1))
M=a Decimal (STR (tmp1)) + a Decimal (STR) (tmp2)
Return m

I_=f.s plit ('. ', 1) [0]
F_=f.s plit ('. ', 1) [1]
F_='0' + f_] [: : - 1

Ii=the reduce (c10, map (to_float, i_))
Ff=the reduce (d10, map (to_float, f_))

Return ii + ff

Print (str2float (s))

CodePudding user response:

The

reference 4 floor rrrr336 reply:

1. Directly using the float function:
 print (float (' 123.45 ')) 
2. Directly using the eval function:
 print (eval () '123.45') 
3. Be sure to practice using the reduce and map can also ah, it feels a bit like its kill chickens:
 the from functools import reduce 
Def str2float (f) : 
S=f.s plit (') 
S1=list (s [0]) 
[1] s2=list (s) 
S2. Reverse () 
S2. Append (' 0 ') 
To_digit=lambda x: int (x) 
C10=lambda x, y: * 10 x + y 
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