一、%占位符
1.說明
# 符號代表意義
%s -- 字符串
%10s -- 指定長度 左填充
%-10s -- 指定長度 右填充
%f -- 浮點數
%.2f -- 保留2位小數點
%d -- 整數
2.實操
a = 'Name'
b = 'Hider'
c = 100
d = 1.80
print("My %s is %s." % (a, b))
# My Name is Hider.
print("My %s is %s. And my age is %d. My height is %f." % (a, b, c, d))
# My Name is Hider. And my age is 100. My height is 1.800000.
%f 默認精度是保留后6位，可通過 %.2f 設置。
print("My %s is %s. And my age is %d. My height is %.2f." % (a, b, c, d))
# My Name is Hider. And my age is 100. My height is 1.80.
字符串長度填充。
# 左填充
print('%10s' % ('Hider')) # Hider
# 右填充
print('%-10s' % ('Hider')) # Hider
二、f-string格式化
f-string 直接使用變量名填充句子當中的內容。
Python 3.6 及以后版本支持 f-string 格式化輸出字符串。優先推薦！！！
a = 'Name'
b = 'Hider'
print(f'My {a} is {b}.')
# My Name is Hider.
print(f'計算結果為：{2*5 + 3*10}')
# 計算結果為：40
string_test = 'ABC'
print(f'It\'s {string_test.lower()}')
# It's abc
三、format關鍵字
1.格式化輸出
format 關鍵字用來格式化輸出字符串。不同入參情況：
- 不指定位置
a = 'Name'
b = 'Hider'
c = 100
d = 1.80
print('My {} is {}.'.format(a,b))
# My Name is Hider.
位置默認開始從 0 計算，然后對應位置填入數據。
- 指定位置
a = 'Name'
b = 'Hider'
c = 100
d = 1.80
print('My {0} is {1}. And my age is {2}.'.format(a,b,c))
# My Name is Hider. And my age is 100.
print('My {1} is {2}. And my age is {0}.'.format(a,b,c))
# My Hider is 100. And my age is Name.
- 關鍵字配對
print('My {a} is {b}. And my age is {c}.'.format(a=10,b=20,c=30))
# My 10 is 20. And my age is 30.
- 字典參數
dic = {'a':10, 'b':20, 'c':30}
print('My {a} is {b}. And my age is {c}.'.format(**dic))
# My 10 is 20. And my age is 30.
- 列表參數
lis = ['a','b','c']
s = 'i like {} and {} and {}.'.format(*lis)
print(s)
# i like a and b and c.
2.精度
pi = 3.1415926535
print('{:.2f}'.format(pi)) # 3.14
print('{:+.3f}'.format(pi)) # +3.142
print('{:.2%}'.format(pi)) # 314.16%
3.千分位分隔符
主要用於貨幣數據的格式化輸出。
a = 1000000000
print('{:,}'.format(a)) # 1,000,000,000
# 添加貨幣符號
print('${:,}'.format(a)) # $1,000,000,000