我已经看到了在简单列表中计算值的解决方案，但是如果你有一个列表列表怎么办？
示例：
list = [[Frank, 23],[Mary, 55],[Craig, 17],[Nancy, 34],[Ben, 55],[Cindy, 47]]
我如何计算每个子列表的第二个值为55的次数？
答案 0 :(得分：2)
假设：
>>> li = [['Frank', 23],['Mary', 55],['Craig', 17],['Nancy', 34],['Ben', 55],['Cindy', 47]]
您可以反转矩阵：
>>> zip(*li)
[('Frank', 'Mary', 'Craig', 'Nancy', 'Ben', 'Cindy'), (23, 55, 17, 34, 55, 47)]
计算第n个元素中的55个：
>>> zip(*li)[1].count(55)
2
或者，您可以使用itemgetter并获取第n项：
>>> from operator import itemgetter
>>> map(itemgetter(1), li)
[23, 55, 17, 34, 55, 47]
>>> map(itemgetter(1), li).count(55)
2
如果您想要所有计数，请使用Counter：
>>> from collections import Counter
>>> Counter(zip(*li)[1])
Counter({55: 2, 17: 1, 34: 1, 47: 1, 23: 1})
答案 1 :(得分：1)
从中创建一个新生成器并将其传递给#define LED1 11
#define LED2 12
#define BUFFER_SIZE 4096
#define SSID "xxxx" // change this to match your WiFi SSID
#define PASS "xxxx" // change this to match your WiFi password
#define PORT "8080" // Port 8080 is default webserver port
char buffer[BUFFER_SIZE];
int n = 0;
String webSite, javaScript, XML, header, content;
void buildWebsite() {
header = "HTTP/1.1 200 OK\r\n";
header += "Content-Type: text/html\r\n";
header += "Connection: close\r\n";
//header += "Refresh: 5\r\n";
buildJavascript();
content = "<!DOCTYPE HTML>\n";
content += javaScript;
content += "<BODY onload='process()'>\n";
content += "<BR>This is the ESP website.<BR>\n";
content += "Runtime = <A id='runtime'></A>\n";
content += "</BODY>\n";
content += "</HTML>\n";
header += "Content-Length:";
header += (int)(content.length());
header += "\r\n\r\n";
webSite = header + content;
}
void buildJavascript() {
javaScript = "<SCRIPT>\n";
javaScript += "var xmlHttp = createXmlHttpObject();\n";
javaScript += "function createXmlHttpObject() {\n";
javaScript += " if(window.XMLHttpRequest) {\n";
javaScript += " xmlHttp = new XMLHttpRequest();\n";
javaScript += " } else {\n";
javaScript += " xmlHttp = new ActiveXObject('Microsoft.XMLHTTP');\n";
javaScript += " }\n";
javaScript += " return xmlHttp;\n";
javaScript += "}\n";
javaScript += "function process(){\n";
javaScript += " if(xmlHttp.readyState == 0 || xmlHttp.readyState == 4){\n";
javaScript += " xmlHttp.open('GET','xml',true);\n";
javaScript += " xmlHttp.onreadystatechange = handleServerResponse();\n"; // no brackets?????
javaScript += " xmlHttp.send();\n";
javaScript += " }\n";
javaScript += " setTimeout('process()',1000);\n";
javaScript += "}\n";
javaScript += "function handleServerResponse(){\n";
javaScript += " if(xmlHttp.readyState == 4 && xmlHttp.status == 200){\n";
javaScript += " xmlResponse = xmlHttp.responseXML;\n";
javaScript += " xmldoc = xmlResponse.getElementsByTagName('response');\n";
javaScript += " message = xmldoc[0].firstChild.nodeValue;\n";
javaScript += " document.getElementById('runtime').innerHTML = message;\n";
javaScript += " }\n";
javaScript += "}\n";
javaScript += "</SCRIPT>\n";
}
void buildXML() {
XML = "<?xml version='1.0' encoding='UTF-8'?>\n";
XML += "<response>\n";
XML += millis2time();
XML += "</response>\n";
}
String millis2time() {
String Time = "";
unsigned long ss;
byte mm, hh;
ss = millis() / 1000;
hh = ss / 3600;
mm = (ss - hh * 3600) / 60;
ss = (ss - hh * 3600) - mm * 60;
if (hh < 10)Time += "0";
Time += (String)hh + ":";
if (mm < 10)Time += "0";
Time += (String)mm + ":";
if (ss < 10)Time += "0";
Time += (String)ss;
return Time;
}
/*******************************************************************
* PROGRAM SETUP
********************************************************************/
void setup() {
delay(1000);
Serial1.begin(115200); // Teensy to ESP8266
Serial.begin(115200); // Teensy to USB Serial
Serial.println("Begin program.");
pinMode(LED1, OUTPUT);
pinMode(LED2, OUTPUT);
// Initialize ESP8266.
setupWiFi();
}
/*******************************************************************
* DEVICE FUNCTIONS
********************************************************************/
// Read line responses from ESP8266.
bool read_till_eol() {
static int i = 0;
if (Serial1.available()) {
buffer[i++] = Serial1.read();
if (i == BUFFER_SIZE) i = 0;
if (i > 1 && buffer[i - 2] == 13 && buffer[i - 1] == 10) {
buffer[i] = 0;
i = 0;
Serial.print(buffer);
return true;
}
}
return false;
}
// Listen for ESP8266 response. By default we are looking for OK\r\n
char OK[] = "OK\r\n";
byte wait_for_esp_response(int timeout, char* term = OK) {
unsigned long t = millis();
bool found = false;
int i = 0;
int len = strlen(term); // compute length of (string)
// wait for at most timeout milliseconds, or if OK\r\n is found
while (millis() < t + timeout) {
if (Serial1.available()) {
digitalWrite(LED2, HIGH);
buffer[i++] = Serial1.read();
if (i >= len) {
if (strncmp(buffer + i - len, term, len) == 0) {
found = true;
break;
}
}
digitalWrite(LED2, LOW);
}
}
buffer[i] = 0;
Serial.print(buffer);
return found;
}
/*******************************************************************
* LOOP
********************************************************************/
void loop() {
int ch_id, packet_len;
char *pb;
// Look for received IDP (unsolicited data packet) from browser refresh.
if (read_till_eol()) {
if (strncmp(buffer, "+IPD,", 5) == 0) // If strings match...
{
// Request: (+IPD, connection channel, data length)
sscanf(buffer + 5, "%d,%d", &ch_id, &packet_len);
if (packet_len > 0) {
// Read serial until packet_len character received
// start from :
pb = buffer + 5;
while (*pb != ':') pb++;
pb++;
if (strncmp(pb, "GET / HTTP", 10) == 0)
{
// Send HTML data.
wait_for_esp_response(2000);
Serial.println("Serving HTML ->");
buildWebsite();
serve(webSite, ch_id);
}
else if (strncmp(pb, "GET /xml", 8) == 0)
{
// Send XML data.
wait_for_esp_response(2000);
Serial.println("Serving XML ->");
buildXML();
serve(XML, ch_id);
Serial.println(millis2time());
}
}
}
}
}
/*******************************************************************
* SEND DATA
********************************************************************/
// Send the data to the ESP8266.
void serve(String data, int ch_id)
{
Serial1.print("AT+CIPSEND=");
Serial1.print(ch_id);
Serial1.print(",");
Serial1.println(data.length());
if (wait_for_esp_response(1000)) {
Serial1.print(data);
}
else {
Serial1.print("AT+CIPCLOSE=");
Serial1.println(ch_id);
}
}
/*******************************************************************
* SETUP WIFI
********************************************************************/
void setupWiFi() {
// Turn on echo.
Serial1.println("ATE1");
wait_for_esp_response(1000);
// Set mode 3 (client + AP).
Serial1.println("AT+CWMODE=3");
wait_for_esp_response(1000);
// Reset WiFi module.
Serial1.print("AT+RST\r\n");
wait_for_esp_response(1500);
// Join AP.
Serial1.print("AT+CWJAP=\"");
Serial1.print(SSID);
Serial1.print("\",\"");
Serial1.print(PASS);
Serial1.println("\"");
wait_for_esp_response(5000);
// Start server.
Serial1.println("AT+CIPMUX=1");
wait_for_esp_response(1000);
// Create TCP Server.
Serial1.print("AT+CIPSERVER=1,");
Serial1.println(PORT);
wait_for_esp_response(1000);
// Set the automatic socket client disconnection timeout from 1 to 28800 seconds.
Serial1.println("AT+CIPSTO=6000");
wait_for_esp_response(1000);
Serial1.println("AT+GMR");
wait_for_esp_response(1000);
Serial1.println("AT+CWJAP?");
wait_for_esp_response(1000);
Serial1.println("AT+CIPSTA?");
wait_for_esp_response(1000);
Serial1.println("AT+CWMODE?");
wait_for_esp_response(1000);
Serial1.println("AT+CIFSR");
wait_for_esp_response(5000);
Serial1.println("AT+CWLAP");
wait_for_esp_response(5000);
Serial1.println("AT+CIPSTATUS");
wait_for_esp_response(5000);
Serial.println("------------------------------------");
}
：
sum()另外，不要将其命名为>>> l = [['Frank', 23],['Mary', 55],['Craig', 17],['Nancy', 34],['Ben', 55],['Cindy', 47]]
>>> sum(item[1]==55 for item in l)
2
，或者屏蔽内置函数list。