Loop statements for basic learning of python introductory

loop statement

In Python, common loop statements are while loop and for loop. A while loop is a loop that repeatedly executes a block of code while a condition is met, while a for loop is a loop that iterates over a sequence.

while loop statement

If the condition is met, it can continue to loop.
Syntax:
while condition:
 When the condition is met, do event 1
 When the condition is met, do event n

Note: The condition needs to get Boolean type, True or False

Example:
Calculate and output the sum of 1 to 100.

i = 1
sum = 0
while i <= 100:
    sum += i
    i += 1
print(f"1到100的和：{
      
      sum}")

Running result: sum of 1 to 100: 5050

Nested use of while loop

while condition 1:
 when condition 1 is met, do thing 1
  when condition 1 is met, do thing n
 while condition 2: when
  condition 2 is met, do thing 1 meet
  condition 2, do thing
n
, the challenge was successful on the 100th day.

i = 1
while i <= 100:
    print(f"今天是开始跳绳的第{
      
      i}天")

    # 内层循环的控制变量
    j = 1
    while j <= 10:
        print(f"今天的跳的第{
      
      j}个")
        j += 1

    print("加油努力坚持")
    i += 1

print(f"坚持到{
      
      i - 1}天，挑战100天每天10个跳绳成功。")

operation result:

The output does not wrap

Add end='' after the output content
Example:

print("Hello", end='')
print("World", end='')

Running result: HelloWorld

output alignment

\t The effect is equivalent to the tab key, which can align multi-line strings
Example:

print("Hello\tWold")
print("Hi\t\tWorld")

operation result:

Comprehensive case:
output and print a nine-nine multiplication table.
Use while loop to print ninety-nine multiplication table

for loop

Polling, processing one by one, until the end.
Syntax:
for temporary variable in data set (sequence) to be processed:
 the code executed when the loop meets the condition

Note:
①The for loop cannot build an infinite loop.
②The data set to be processed (that is, the sequence type) can be a string, a list, a tuple, etc.
Example:

# 遍历name中有多少个a
name = "I am a hardworking girl"
count = 0
for x in name:
    if x == "a":
        count += 1

print(f"{
      
      name}中共有：{
      
      count}个a。")

Running results: There are 3 a's in I am a hardworking girl.

range statement

①range
Get the sequence of numbers starting from 0 and ending with num, excluding num itself
Example: range(3) gets 0, 1, 2

②range(num1，num2)
Get the sequence of numbers starting from num1 and ending with num2, excluding num2 itself
Example: range(1,3) gets 1, 2

③range(num1，num2，step)
Example: get the sequence of numbers starting from num1 and ending with num2, excluding num2 itself,
and the step size between numbers is based on step, and step defaults to 1
example: range(5,10,2) gets 5,7,9
comprehensive case:

# range(num)
for x in range(10):
    print(f"{
      
      x}\t", end='')
print()  # print(),输出一个换行

# range(num1,num2)
for x in range(5, 10):
    print(f"{
      
      x}\t", end='')
print()  # print(),输出一个换行

# range(num1,num2,step)
for x in range(5, 10, 2):
    print(f"{
      
      x}\t", end='')
print()  # print(),输出一个换行

# 打印10个加油
for x in range(10):
    print(f"加油\t", end='')

operation result:

Nested use of for loops

for temporary variable in data set to be processed (sequence):
 code 1 executed when the loop meets the condition
 n
 for temporary variable in data set to be processed (sequence):
  code 1 executed when the loop satisfies the condition Example
  of code n executed when the loop meets the condition
:
the output prints a nine-nine multiplication table.
Use for loop to print ninety-nine multiplication table

continue and break interrupt the loop

continue: interrupt this loop and go directly to the next one (temporary interruption)
break: interrupt the entire loop (permanent interruption)
Points to note: When nested, it can only take effect on the loop of the current layer, and does not affect the loop of the upper layer.
Example:

for i in range(1, 5):
    print(f'今天是第{
      
      i}天')
    continue
    print(f'今天是第{
      
      i}天')  # 总共循环4次，此句都不会执行

for i in range(1, 5):
    print(f'明天是第{
      
      i}天')
    break
    print(f'明天是第{
      
      i}天')  # 总共循环1次，此句不会执行

Running results:

comprehensive case:
use for loop combined with continue, break to complete scholarship distribution