从标准输入读取浮点值并在time.sleep中使用

Question

I'm currently struggling with simple code, it works with seconds but I want to allow users to use minutes instead, which is much easier. Here it is:

import time
import os
import math
import subprocess

input1 = raw_input("Broj minuta:")
min = input1 * 60
min1 = float(min)
print min1
time.sleep(min1)
os.system("shutdown")

I get this error:

Broj minuta:2
Traceback (most recent call last):
  File "timer.py", line 8, in <module>
    time.sleep(min)
TypeError: a float is required

When I try to convert it to float using code below, it says that sleep time is big, and it is, if I choose 2 minutes I get:

min = input1 * 60
min1 = float(min)

Broj minuta:2
2.22222222222e+59
Traceback (most recent call last):
File "timer.py", line 10, in <module>
   time.sleep(min1)
OverflowError: sleep length is too large

Answer 1

input1 = raw_input("Broj minuta:")

raw_input returns a string. You need to convert that to a number, like this

input1 = int(raw_input("Broj minuta:"))

If you don't do this, let say if you enter 2 , it will still be a string and you are doing

input * 60

which means '2' * 60 , which is equal to '222222222222222222222222222222222222222222222222222222222222' and it is still a string. That's why time.sleep(min) complains that

TypeError: a float is required

In the second case, you are converting '222222222222222222222222222222222222222222222222222222222222' to a float properly, but the value is 2.22222222222e+59 , which is tooo big for time.sleep .

Answer 2

(Your traceback must be out of date; it shows time.sleep(min) (in which case the error is justified), but your code has time.sleep(min1) .)

The issue is that the result of raw_input is a string. When you write input1 * 60 , you repeat the string 60 times (ie instead of 120, you get '222222222222222222222222222222222222222222222222222222' ).

Answer 3

You're performing the conversion too late. input1 is a string, and multiplying a string by an integer

min = input1 * 60

does string repetition: '12' * 60 == '12121212...

Instead, convert to float, then multiply:

min = float(input1) * 60

Answer 4

The variable returned by raw_input is a string. To add more information to what is happening in your code, here is an example session.

In [1]: i = raw_input("Something")
Something20

In [2]: i
Out[2]: '20'

In [3]: type(i)
Out[3]: str

In [4]: i*60
Out[4]:     '202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020'

In [5]: float(i*20)
Out[5]: 2.02020202020202e+39

Out [2] shows the string '20' . This is confirmed when we check the type of i , which is str . Now, in Python, when you multiply a string with a number x , you get a string with x times the original string repeated.

This is what was happening in your code. Thus, as suggested in the other answer, you need to cast your input to a float.

Another, way of doing this (on Python 2.x) is to NOT use raw_input() and instead use input()

In [6]: j = input('Something else?')
Something else?20

In [7]: j
Out[7]: 20

In [8]: j*60
Out[8]: 1200