3.字符串

1.字符串的格式化输出　

name = input("姓名:")
age = input("年龄:")
# str = "我叫" + name + ",我今年" +age
# print(str)
# 1 format(推荐)
text = "我叫{0},我今天{1}岁".format(name, age)  #占位符
print(text)

# 2. %
text1 = "我叫%s,我今天%d" %("aaa", 10)
print(text1)


str1 = "union is good man"

2.字符串独有功能

#   字符串独有的功能
#   - 大小写
#   - 开头、结尾
#   - 切割
#   - 连接
#   - 替换
#   - 是否是数字
#   - 除去空白

str1 = "union is good man"
# 1.
# upper() 大写
# lower() 小写
print(str1.upper())
print(str1.lower())

# 2
# isdecimal : 判断是不是整数
v1 = "123"
res = v1.isdecimal()

print(res)

# 3
# startswith/endswith : 是否以xxx开头/xxx结尾
add = input("请输入地址:")
if add.startswith("北京"):
    print("京户")
else:
    print("非京户")

# 4
# replace:替换
text = "中国"
data = text.replace("中国", "新中国")
print(data)

text1 = input("请输入评论:")
data1 = text1.replace("移动", "xxx")
print(data1)

# 5. split|rsplit(从右往左切) : 切割,可以把字符串按照某种格式进行切割,其输出结果类型为list
str1 = "union is a good man"
str2 = str1.split(" ")   # str2被切成了列表
print(str2)

test = input("请输入文件名:")
data = test.rsplit(".", maxsplit=1)
print(data[0])
print(data[1])

info = input("用户和密码:")
data_list = info.split(",", maxsplit=1)
if data_list[0] == "root" and data_list[1] == "123":
    print("登录成功")
else:
    print("登录失败")

# 6.join 连接(拼接)
v1 = ["张三", "李四", "周五"]
data_list = "_".join(v1)
print(v1)

# 动态注册用户到列表
user_list1 = ["张三", "李四"]
data_str = ",".join(user_list1)
text = "平台注册用户有{0}".format(user_list1)
print(text)

# 7. maketrans
t46 = str.maketrans("ac", "65")
str47 = "aron is a good man"
str48 = str47.translate(t46)
print(str48)

# 8.解码|编码
# encode
data2 = "union is a good man"
str53 = data2 .encode("utf-8")
print(str53)

# 9.strip|lstrip|rstrip :去除空白(头部和尾部),lstrip取出左边空白，rstrip除去右边的空白
info = "中国联通 "
data = info.strip()
print(data)

# 字符串的公共功能
# 1.长度 、2.索引[0] [-1]、3.切片[2:4]
name = "union is a nice man"
name_len = len(name)
print(name_len)
print(name[0])

# 索引
name = "union is nice man"
index = 0
while index < len(name):
    item = name[index]
    print(item)
    index += 1
# 切片
name = "union is nice man"
print(name[2:4]) # 前取后不取

练习题：

# 练习题

# 代码实现,提示用户输入文本,是以中国开头,输出中国人，否则外国人
info = input("请输入x:")
if info.startswith("中国x"):
    print("中国人")
else:
    print("外国人")

# 写代码,用户文本，文本中上替换下
text = input("地址是:")
data = text.replace("上", "下")
print(data)

# 提示用户输入文本, 计算文本中"国"出现的次数
text1 = input("信息:")
count = 0
for i in text1:
    if i == "国":
        count += 1
print("国的出现次数为{0}".format(count))

# 用户输入文本,含有数字和字母 fdafafas123weqr,将里面的数字提取出来
text2 = input("输入:")
result = ""
data_list = []
for item in text2:
    if item.isdecimal():
        result = result + item
        data_list.append(item)

print(result)
print(data_list)
print("".join(data_list))

# 输入电脑路径,程序自动寻找整个路径下所有的mp4后缀的文件
path = input("路径:")
file_list = os.listdir(path)
for name in file_list:

    group = name.rsplit(".", maxsplit=1)
    print(group[-1])

# 判断某个字符串是否包含某个子序列
test = "中国北京上海神州"
if "中国" in test:
    print("在里面")
else:
    print("不在里面")