【 Python 】 Python的字符串操作（读取/合并/修改/删除/占位符等）

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# 1 字符串的读取
sayHello = 'Hi,my name is Nick!'
# 每个字符对应一个索引(Index)，可以通过索引读取对应值
sayHello[2]
# 值为','

sayHello[2:4]
# 该属性为左闭右开区间，所以值为',m'

sayHello[:5]    # 读取下标 0~5 的值'Hi,my'

sayHello[:]     # 读取字符串所有值

sayHello[0:10:2]   # [左下标：右下标：步长]带步长读取 'H,ynm'

sayHello[-1]       # 读取倒数第一个值，依次类推
sayHello[-4:-1]    # 同为左闭右开区间  'ick'

# 2 字符串的合并
name = 'Nick'
sex = 'man'
sayHi = name + ' is a ' + sex   # 用加号合并三个字符串
print(sayHi)                    # 'Nick is a man'

# 3 字符串值的修改
cat = 'Three cats'
dog = cat[:6] + 'dogs'  # 读取子字符串再合并
print(dog)
# 不可以使用 cat[6:]='dogs'，会报错

# 4 字符串的删除
del cat   # 清除内存中的cat，再次调用会报错

# 5 原始字符串控制
print(r'C:\back\nick')  # 特殊转义符不起作用

# 6 重复输出字符串(*)
print('Nick is handsome'*2)

# 7 占位符
merit = 'handsome'
age = 25.4
print('Nick is {0}'.format(merit))
print("Nick's age is %d" % age)     # %d 格式为整数
print("Nick is %s and he is so %s" % (age, merit))  # %d 依次占位
# Nick is handsome
# Nick's age is 25
# Nick is 25.4 and he is so handsome