int, bool, str method, for loop

day03 notes

1. Integer and Boolean values

2. Detailed string (common methods

3.for cycle

1. Integer and Boolean values

python3: in

python2: int, long (long integer)

num = 15
print(num.bit_length())
结果为4

十进制 -- 二进制
# 15  1
# 7   1
# 3   1
# 1   1
# 0
# 34(十进制)
# 32 16 8 4 2 1
# 1   0 0 0 1 0
二进制 -- 十进制
# 1*2**0 + 0*2**1 + 1*2**2 + 0*2**3 + 1*2**4 + 1*2**5
# 1 + 0 + 4 + 0 + 16 + 32
# 45 十进制转二进制
# 32 16 8 4 2 1
# 1  0  1 1 0 1

bin -- 将十进制转换成二进制
print(bin(45))
int -- 将二进制转换成十进制
print(int("101101",2))
print(int(0b101101))

Boolean value:

Type Conversion

Only numbers 0 is False, the rest are True

String as long as the content is True, no content is False

print(bool(""))

print(type(str(False)))

print(int(True))

print(int(False))

2. Detailed strings

s = "meet"

String element (alpha)

String: store some data

Strings are ordered

Strings are immutable

Index: accurately and quickly find value

s = "meet"

0123 # # right to left, left to right -4-3-2-1

s [0] # find elements by index accurately

slice:

Care regardless of

print (s [0:10]) # [starting index: Index termination]

print (s [-6:]) # [starting index: default content acquisition end of the string]

print (s [:]) # [default content acquisition start of the string: the default content acquisition end of the string]

Compared:

s = "alex_wusir|oldboy"

index:

print (s [20]) # error: string index out of range out of range index being given

slice:

print (s [1: 100]) # slice without error index exceeds

Steps

s = "alex_wusir|oldboy"

print(s[0:5:2])

Step 1 by default starting index: End Index: step

Step step may decide the search direction and the pace, the n may take, may be taken backwards

Palindrome

Shanghai water from the sea

while True:
    msg = input("请输入内容:")  # 12321#     
    if msg == msg[::-1]:       # 将字符串进行反转#         
        print("这是回文")#     
    else:
        print("请重新输入!")

3. The method of operation of the string

s1 = s.strip()

Default remove head and tail ends of the spaces and line breaks, tabs (Tab) *****

s1 = s.strip("a")

s2 = s1.split("+")

The default split by spaces, line breaks, tabs, returns a list of

s1 = s.split ( "-", maxsplit = 1) is not specified by default all divided maxsplit

s1 = s.replace("n","s",1)

Replace (old, new, Replace Occurrence)

Filter grateful word

s = "TMD"
msg = input(">>>") 
if s in msg:
    msg = msg.replace(s,len(s) * "*")  # len求长度# 
print(msg)

1. To achieve a calculator, the calculator supports only addition and subtraction, only three numbers, for example, supports (11 + 22--12)

s = input("请输入要计算的公式:")
s1 = s.replace("-","+-")
s2 = s1.split("+") # s2是一个列表,列表支持索引
print(int(s2[0]) + int(s2[1]) + int(s2[2]))

s1 = s.upper()

ALL CAPS

s2 = s.lower()

All lowercase

验证码不区分大小写
s = "XbGj"
msg = input("请输入验证码(XbGj):")
if msg.upper() == s.upper():
    print("成功！") 
else:
    print("失败")

import random  # 随机数
ascii
48 - 57 数字
65 - 90 大写
97 - 122 小写
print(chr(97)) # 通过十进制查找编码上对应的字符
自动生成验证码:
s = f"{chr(random.randint(48,57))}{chr(random.randint(65,90){chr(random.randint(97,122))}{chr(random.randint(48,57))}" # 4位
msg = input(f"请输入验证码{s}:")
if msg.lower() == s.lower():
    print("验证成功!")
else:
    print("验证失败")

s1 = s.count("e")

Counting statistics

print(s.startswith("x",3))

Judgment begins with what - returns a Boolean value

print(s.endswith("r"))

Judgment as to what the end - returns a Boolean value

series is

s = "123 Hello aaaa"

print (s.isalpha ()) # judgment is not letters, Chinese composition - returns a Boolean value

print (s.isdigit ()) # determine whether it is digital - bug

print (s.isdecimal ()) # determines whether the number of decimal

print (s.isalnum ()) # determines whether the letters, numbers, characters

4.for cycle

for循环
固定结构:
for i in 可迭代对象:
    循环体

s = '6314'
for i in s:
    print(i)
print(i)

面试题
s = '123'
for i in s:
    pass # 占位
print(i)

思维 : 借助了你的循环次数
s = "12"
for i in s:  # 1    2
    print(s) # 12   12

Iterables: removing (int - Integer; bool - Boolean)

s = '321'
for i in s:
    print('倒计时'+i)
count = 0
while count < len(s):
    print('倒计时%s'%s[count])
    count += 1