如何重复while循环一定次数

Question

As seen over here , there are two ways to repeat something a number of times. But it does not seem to work for me, so I was wondering if anybody could help.

Basically, I want to repeat the following 3 times

 import random
 a = []
 w = 0

 while w<4:
     x = random.uniform(1,10)
     print(x)
     print(w)
     a.append(w+x)
     print(a)
     w=w+1

Based on what the link says, this is what I did,

 import random
 a = []
 w = 0
 r = 0


 while r < 3: 
      while w<4:
          x = random.uniform(1,10)
          print(x)
          print(w)
          a.append(w+x)
          print(a)
          w = w+1
      r += 1

But this doesn't seem to work. The while loop only repeats once instead of three times. Could anybody help me fix this problem?

Answer 1

I dont see the

w=w+1

in your code, why you removed that? Add w=w+1 before r=r+1 .

Good luck.

Answer 2

As stated by @R2RT, you need to reset w after each r loop. Try writing this:

import random
 a = []
 w = 0
 r = 0


 while r < 3: 
      while w<4:
          x = random.uniform(1,10)
          print(x)
          print(w)
          a.append(w+x)
          print(a)
          w = w+1
      r += 1
      w = 0

Answer 3

To repeat something for a certain number of times, you may:

1. Use range or xrange

    for i in range(n): # do something here 

2. Use while

    i = 0 while i < n: # do something here i += 1 

3. If the loop variable i is irrelevant, you may use _ instead

    for _ in range(n): # do something here _ = 0 while _ < n # do something here _ += 1 

As for nested while loops, remember to always keep the structure:

i = 0
while i < n:

    j = 0
    while j < m:
        # do something in while loop for j
        j += 1

    # do something in while loop for i
    i += 1