Python String Formatting
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format() method allows you format string in any way you want.
Syntax: template.format(p1,p1,...
template is a string containing format codes, format() method uses it’s argument to substitute value for each format codes. For e.g
1 | >>>'Sam has {0} red balls and {1} yellow balls'.format(12,31) |
{0} and {1}
Expected Output:
1 | Sam has12red balls and31yellow balls |
This technique is okay for simple formatting but what if you want to specify precision in floating point number ? For such thing you need to learn more about format codes. Here is the full syntax of format codes.
Syntax: {[argument_index_or_keyword]:[width][.precision][type]}
type can be used with format codes
Format codes | Description |
---|---|
d | for integers |
f | for floating point numbers |
b | for binary numbers |
o | for octal numbers |
x | for octal hexadecimal numbers |
s | for string |
e | for floating point in exponent format |
Following examples will make things more clear.
Example 1:
1 | >>>"Floating point {0:.2f}".format(345.7916732) |
Here we specify 2 digits of precision and f is used to represent floating point number.
Expected Output:
1 | Floating point345.79 |
Example 2:
12 | >>>importmath>>>"Floating point {0:10.3f}".format(math.pi) |
Here we specify 3 digits of precision, 10 for width and f for floating point number.
Expected Output:
1 | Floating point3.142 |
Example 3:
1 | "Floating point pi = {0:.3f}, with {1:d} digit precision".format(math.pi,3) |
here d in {1:d} represents integer value.
Expected Output:
1 | Floating point pi=3.142,with3digit precision |
You need to specify precision only in case of floating point numbers if you specify precision for integer ValueError will be raised.
Example 5:
1 | 'Sam has {1:d} red balls and {0:d} yellow balls'.format(12,31) |
Expected Output:
1 | Sam has31red balls and12yellow balls |
Example 6:
1 | "In binary 4 is {0:b}".format(4)# b for binary, refer to Fig 1.1 |
Expected Output:
1 | Inbinary4is100 |
Example 7:
12 | array=[34,66,12]"A = {0}, B = {1}, C = {2}".format(*array) |
Expected Output:
1 | 'A = 34, B = 66, C = 12' |
Example 8:
1234 | d={'hats':122,'mats':42} |
Expected Output:
1 | "Sam had {hats} hats and {mats} mats".format(**d) |
format() method also supports keywords arguments.
1 | 'Sam has {red} red balls and {green} yellow balls'.format(red=12,green=31) |
Note while using keyword arguments we need to use arguments inside {} not numeric index.
You can also mix position arguments with keywords arguments
12 | 'Sam has {red} red balls, {green} yellow balls \and {0} bats'.format(3,red=12,green=31) |
format() method of formatting string is quite new and was introduced in python 2.6 . There is another old technique you will see in legacy codes which allows you to format string using % operator instead of format() method.
Let’s take an example.
1 | "%d pens cost = %.2f"%(12,150.87612) |
Here we are using template string on the left of % . Instead of {} for format codes we are using % . On the right side of % we use tuple to contain our values. %d and %.2f are called as format specifiers, they begin with % followed by character that represents the data type. For e.g %d format specifier is a placeholder for a integer, similarly %.2f is a placeholder for floating point number.
So %d is replaced by the first value of the tuple i.e 12 and %.2f is replaced by second value i.e 150.87612 .
Expected Output:
1 | 12pens cost=150.88 |
Some more examples
Example 1:
New: "{0:d} {1:d} ".format(12,31)
Old: "%d %d"%(12,31)
Expected Output:
1 | 1231 |
Example 2:
New: "{0:.2f} {1:.3f}".format(12.3152,89.65431)
Old "%.2f %.3f"%(12.3152,89.65431)
Expected Output:
1 | 12.3289.654 |
Example 3:
New: "{0:s} {1:o} {2:.2f} {3:d}".format("Hello",71,45836.12589,45)
Old: "%s %o %.2f %d"%("Hello",71,45836.12589,45)
Expected Output:
1 | Hello10745836.1345 |
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side serve col temp mes eth this add access One particularly useful string method is format. The format method is used to construct strin
Remember the Zen of Python and how there should be “one obvious way to do something in Python”? You might scratch your head when you find out that there (Sponsors) Get started learning Python with DataCamp's free Intro to Python tutorial. Learn Data Science by completing interactive coding challenges and tro -type error: where mat obj AS print %s Where?
運行Python程序,報錯出現在這一行 return "Unknow Object of %s" % value
Why?
%s 表示把 value變量裝換為字
source: https://realpython.com/python-f-strings/
As of Python 3.6, f-strings are a great new way to format strings. Not only are they more read
As of Python 3.6, f-strings are a great new way to format strings. Not only are they more readable, more concise, and less prone to error than other way
前言
在學習python中難免犯下一些幼稚的錯誤,為了方便後來人的學習,寫下此篇文件。
問題
TypeError: not all arguments converted during string formatting
舉例
例如:
>>> cur.execute("INSERT INTO foo VALUES (%s)", "bar") # WRONG
>>> cur.execute("INSERT INTO foo VALUES (%s)", ("bar")) 一次 pan bcd 索引 col def 第一次 art -1 2017-07-03 23:26:08
1、.replace(self, old, new, count=-1)
replace()函數將舊字符串替換為新字符串,最後一個參數count為可選項,表示替換最多c str upper enter wap abs final ace style 學習 嗯,學習其它語言沒這樣全練過,嘻嘻
//test.py
1 # -*- coding: UTF-8 -*- 2 3 str = "i am worker" 4 print str. capi pan span sta string 第一個 cnblogs div 居中
str.capitalize() # 將字符串的第一個字母變成大寫,其他字母變小寫。對於 8 位字節編碼需要根據本地環境
>>> ‘hello‘.capitaliz 否則 字符連接 ring 新的 包含 world spa bsp 技術 1. Python isalnum()方法 #檢測字符串是否由字母和數字組成
如果 string 至少有一個字符並且所有字符都是字母或數字則返回 True,否則返回 False
>>& tin convert str 就是 ring erro 說明 mat uri print ("So, you‘re 5r old, %r tall and %r heavy." % (age, height, weight))
print ("So, you‘re %r python string方法 描述string.ljust(width)返回一個原字符串左對齊,並使用空格填充至長度 width 的新字符串\>>> x.ljust(20)‘Hello,wold ‘
string.center(width)返回一個原字符串居中,並使用空格填充
字串常量
>>> import string
>>> string.ascii_uppercase
'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
>>> string.ascii_lowercas
string.Template,將一個string設定為模板,通過替換變數的方法,最終得到想要的string。
1. 用法示例
(改寫 from python官方文件):
>>> from string import Template
>>>
python strip() 函式和 split() 函式的詳解及例項
python strip() 函式和 split() 函式的詳解及例項
一直以來都分不清楚strip和split的功能,實際上strip是刪除的意思;而split則是分割的意思。因此也表示了這兩個功能是完全不一樣的, code upper class spa string port python 打印 註意
In [1]: import string
In [2]: string.lowercase # lowercase用於打印所有小寫字母,註意這是string模塊的一
python join 和 split方法的使用,join用來連線字串,split恰好相反,拆分字串的。
1.join用法示例
>>>li = ['my','name','is','bob']
>>>' '.join(li)
Python 字串去掉標點符號最佳實踐
方法一:
str.isalnum:
S.isalnum() -> bool
Return True if all characters in S are 相關推薦
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