Python笔记（1）----条件、循环语句

1，if条件语句

    if 判断条件：

         执行语句

    else:

         执行语句

num = 3
if num < 5:
print "yes"
else:
print "no

条件较多时可以用or或者and,and(同时成立)、or(一个成立即可)。

if (num > 1 and num < 5) or (num > 6 and num < 9):

    print "yes"

else:

    print "no"

2，while循环语句

 

 while 判断条件：

      执行语句

count = 0

while (count < 9):

    print"the count is:",count

    count = count + 1

print "good bye"

while语句的continue、break命令

i=1

while i <10:

    i +=1

    if i%2>0:

        continue

    print i

i=1

while 1:

    print i

    i+=1

    if i>10:

        break

while 无线循环

v = 1

while v == 1:

    num = raw_input("Enter a number : ")

    print "You entered: ", num

while.....else循环

c = 0

while c < 5:

    print c, "is less than 5"

    c = c + 1

else:

    print c, " is not less than 5"

3，for循环

  

for interating_var in sequence:

    statements(s)

fruits = ['banana','apple','mango']

for fruit in fruits:

    print "current fruit:",fruit

通过索引执行循环

fruits = ['banana','apple','mango']

for index in range(len(fruits)):

    print "current fruit:",fruits[index]

注：range()返回一个序列数，len()返回列表的长度。

for....else

for num in range(10,20):

    for i in range(2,num):

        if num % i == 0:

            j = num/i

            print "%d equal %d * %d" % (num ,i,j)

            break

    else:

        print num, "is a prime number"

4,循环嵌套

i = 2

while(i < 100):

    j = 2

    while(j <= (i/j)):

        if not(i%j):

            break

        j = j + 1

    if (j > i/j):

          print i, "is a prime number"

    i = i + 1

print "Good bye!"

pass语句

for letter in 'Python':

   if letter == 'h':

      pass

      print 'this is pass block'

   print 'current letter :', letter

print "Good bye!"