除法模块

Author: qiwsir

divide.py

@@ -0,0 +1,61 @@
+#! /usr/bin/env python
+#coding:utf-8
+
+def divide(numerator, denominator, detect_repetition=True, digit_limit=None):
+
+    # 如果是无限小数，必须输入限制的返回小数位数:digit_limit
+    # digit_limit = 5，表示小数位数5位，注意这里的小数位数是截取，不是四舍五入.
+    if not detect_repetition and digit_limit == None:
+        return None
+
+    decimal_found = False
+                                
+    v = numerator // denominator
+    numerator = 10 * (numerator - v * denominator)
+    answer = str(v)
+                                                
+    if numerator == 0:
+        return answer
+                                                              
+    answer += '.'
+    
+    # Maintain a list of all the intermediate numerators
+    # and the length of the output at the point where that
+    # numerator was encountered. If you encounter the same
+    # numerator again, then the decimal repeats itself from
+    # the last index that numerator was encountered at.
+    states = {}
+    
+    while numerator > 0 and (digit_limit == None or digit_limit > 0):
+        
+        if detect_repetition:
+            prev_state = states.get(numerator, None)
+            if prev_state != None:
+                start_repeat_index = prev_state
+                non_repeating = answer[:start_repeat_index]
+                repeating = answer[start_repeat_index:]
+                return non_repeating + '[' + repeating + ']'
+            states[numerator] = len(answer)
+
+        v = numerator // denominator
+        answer += str(v)
+        numerator -= v * denominator
+        numerator *= 10
+        if digit_limit != None:
+            digit_limit -= 1
+            
+            
+    if numerator > 0:
+        return answer + '...'
+    return answer
+
+if __name__=="__main__":
+    print "5divide2",
+    print divide(5,2)
+    print "10divide3",
+    print divide(10,3)
+    print divide(10,3,5)
+    print "15divide7"
+    print divide(15,7)
+    print divide(15,7,True,3)
+