21 22 py中的while for循環

第八課 while循環
# coding:utf-8

# while循環

# 當布爾表達式爲True，就是執行一遍循環體中的代碼。
'''
如今要從1 輸出到 10 
print(1)
print(2)
print(3)
print(4)
print(5)
print(6)
print(7)
print(8)
print(9)
print(10)

'''
'''
while condition_expression:
    statement1
    statement2
    ... ...
    statementn

otherstatement
'''
# 從1 輸出到 10  
x = 1
while x <= 10:
    print(x)
    x += 1 # 這一行的代碼至關於 x = x +1  輸出的結果爲：1..10

x = 1
while x <= 10:
    x += 1 # 這一行的代碼至關於 x = x +1 
    print(x)    #輸出的結果爲 1..11   這裏注意一下

shell 中的while循環 
[hadoop@dev-hadoop-test03 majihui_test]$ cat b.sh
#!/bin/bash
x=1

while (( x <= 10 ))
do
       echo "$x"
        ((x = x+1)) 
done
[hadoop@dev-hadoop-test03 majihui_test]$ sh b.sh 
1
2
3
4
5
6
7
8
9
10

[root@localhost day9]# cat while02.sh 
#!/bin/bash
i=1
sum=0
while (( i <= 100 ))
do
        ((sum=sum+i))
        ((i=i+1))
done
printf "totalsum is :$sum\n"
[root@localhost day9]# sh while02.sh  
totalsum is :5050

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第九課 for循環
for循環爲了簡化代碼，通常來講，相同的實現 while可能須要更多的代碼行來實現 

# coding:utf-8

numbers = [1,2,3,4,5,6,7,8,9,10]   # 定義一個序列的列表 

# 使用while循環  經過索引 
i = 0
while i < 10:
    print(numbers[i], end=" ") #已空格爲分隔符 輸出結果爲 1 2 3 4 5 6 7 8 9 10
    i += 1
print()         # 這個的意思表示換行
# 使用for循環
for num in numbers:
    print(num, end = " ") # 結果爲 1 2 3 4 5 6 7 8 9 10 
print()         # 這個的意思表示換行

#  從1到1000循環 用for
numberss = range(1,100)     # 先產生一個範圍 
for numm in numberss:
    print(numm, end=",")
print()

names = ["Bill", "Mike", "John", "Mary"]

for i in range(0, len(names)):
    print(names[i], end=" ") #輸出結果爲 Bill Mike John Mary 

print()
for i in range(len(names)):
    print(names[i], end=" ") #輸出結果爲 Bill Mike John Mary 
# 這兩種的寫法都是同樣的

shell中的for循環：
[root@localhost day10]# cat for01.sh  
#!/bin/bash
for i in 5 4 3 2 1
do
        echo $i
done
[root@localhost day10]# cat for02.sh 
#!/bin/bash
for i in {5..1} 
do
        echo $i

done
[root@localhost day10]# sh for01.sh 
5
4
3
2
1
下面這個是我常常去清空批量的日誌執行的語句 
for n in `ls cloudera-scm-server.log*`;do echo "" > $n;done