Python branch loop: if elif for while

Python indentation represents a level in a recommended four spaces

Branch and loop

Branch condition is circulating in the most central point, solve the problem scenario is different problems have different processing logic. When the conditions are satisfied, or a single or multiple branching and looping into the condition is not satisfied, the process will be described here on the basis of the same logic Executive dynamic change specific parameters, thereby generating a variety of possibilities, but requires a possibility must perform other wherein possibility need not be performed when using branches.

The core loop is a boundary value, the control execution frequency of boundary value control cycle, the logic loop is repeated until reaching the limit value executed, out of the loop.

In Python not form scope branching and looping, branching, and form a loop in scope as Golang other languages. Python No ++ - increment decrement the operator, and is used for loop iteration data can traverse.

Branched and cyclic specification:

Is not recommended to write a lot of code at a logic branching and looping, or a function package few lines of code to write a small amount of

Branch - if elif

number = 10
 
if number >= 100:
    print("Hai")
elif 50 <= number < 100:
    print("Hello")
else:
    print("OK")

-For cycle

students = ["QiNiuYun", "BaiDu", "WeiChat", "AliYun"]
for student in students:
    print(student)

-While cycle

'''
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'''
start = 0
while start <= 100:
    print(start)
    start += 1

Loop flow control

contine this cycle begins, i.e. this line contine back loop are no longer performed, restarting the loop to enter is determined from the condition

start = 0
while start < 100:
    start += 1
    if start % 2 == 0:
        continue
    print(start)

break this end of the whole cycle, which is performed from this line after the break, the loop out of the loop execution, the execution cycle behind the logical structure

'''
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'''
start = 0
while start < 100:
    start += 1
    if start > 50:
        break
    print(start)

Usually joint break and contine branches special cases flow control loop

Variable iterables joint in general for loop

The iterables str list tuple set dict range emumerate __ getitem__

Traversal str

name = "beimenchuixue"
 
for rune in name:
    print(rune)　　

Traversal list

'''
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'''
names = ["QiNiuYun", "BeiMenChuiXue", "AliYun", "BaiDu"]
 
for name in names:
    print(name)

Traversal tupe

platforms = ("Linux", "MAC", "Windows", "Android", "IOS")
 
for platform in platforms:
    print(platform)

Traversal set

languages = {"zh_CN", "en_US"}
for language in languages:
    print(language)

Traversal dictionary dict

'''
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'''
info = {"name": "BeiMenChuiXue", "age": 18, "sex": "male", "phone_number": "15570910000"}
 
for key in info:
    # 在字典的遍历中，只能获取字典的key值
    print(key, info[key])

Traversing range

for number in range(1, 100, 2):
    # 从1开始到100,但不包括100,间隔步长为2
    print(number)

Traversal emumerate

names = ["QiNiuYun", "BeiMenChuiXue", "AliYun", "BaiDu"]
 
for name in enumerate(names):
    # emumerate 索引从0开始计数，返回一个由索引和值组成的元组
    print(name)

Traversal __ gettiem__

'''
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'''
class Class(object):
    def __init__(self, student_names):
        self.student_names = student_names
 
    def __getitem__(self, item):
        return self.student_names[item]
 
 
python_class = Class(["QiNiuYun", "BeiMenChuiXue", "AliYun", "BaiDu"])
 
for python_student in python_class:
    # for循环会去找 __getitem__魔法方法，每次从 0 开始步长为1向 __getitem__传递 参数
    # 如果 __getitem__触发异常，for会处理异常并退出循环
    print(python_student)

Use a dictionary to achieve Go language switch

def connect():
    print("connect")
 
 
def conn():
    print("conn")
 
 
def default_conn():
    print("default_conn")
 
 
interface = {"connect": connect, "conn": conn}
interface.get("conn", default_conn)()
interface.get("", default_conn)()