擅长:python、mysql、java
<pre><code>def get_float(prompt):
while True:
try:
return float(input(prompt))
except:
print "Thats not a number!"
def get_positive_number(prompt,tries=3):
for i in range(tries):
result = get_float(prompt)
if result >= 0: return result
print "Sorry Negative not allowed %d/%d"%(i,tries)
while True:
result = get_positive_number("How Many Gallons?")
if result is None:
print "OK DONE"
break
print "Convert %0.2f Gallons"%(result)
</code></pre>