for 循环：
for 循环用于迭代序列（即列表、元组、字典、集合或字符串）。

语法：
对于序列中的变量

示例：

txt = '1234'

for num in txt:
    print(num,end=' ')

output:
1 2 3 4

如果条件：
if 语句的工作原理是检查表达式以查看是否满足条件，并根据获得的输出返回一个值。

syntax:
if condition:
      if condition is true
else:
      if condition is false

示例

x=20
if x>=20:
   print(x is within 20)
else :
   print(x is above the limit)

output:
x is within 20

txt = '12a4'

for num in txt:
    if num>='0' and num<='9':
        print(num,end=' ')
    else:
        print('not decimal',end=' ')

output:

1 2 not decimal 4
above code is the example of combines if and for.

name = input("请输入您的名字：")
打印（姓名）
名称中的字母：
print(字母表, end='*')

输出：
r*a*j*a

代码检查每个索引并打印输出。

name1 = input("Enter the first name: ")
name2 = input("Enter the second name: ")
name3 = input("Enter the third name: ")
name4 = input("Enter the fourth name: ")
name = [name1, name2, name3, name4]


for letter in name:
    if letter[0]=='G':
        print(letter)
    else:
        continue
for alphabet in name:
    if alphabet[-1]=='a':
        print(alphabet)
    else:
        continue
for alpha in name:
    for i in alpha:
        if i==' ':
            print(alpha)
        else:
            continue
for character in name:
    if len(character)>9:
        print(character)
    else:
        continue

output:

Enter the first name: Guhanraja
Enter the second name: Lakshmi Pritha
Enter the third name: Guru Prasanna
Enter the fourth name: Varatharajan
Guhanraja
Guru Prasanna
Guhanraja
Lakshmi Pritha
Guru Prasanna
Lakshmi Pritha
Guru Prasanna
Lakshmi Pritha
Guru Prasanna
Varatharajan

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